From pieterh@sci.kun.nl Fri Sep 22 14:57:28 1995 Return-Path: Received: from wn1.sci.kun.nl (wn1.sci.kun.nl [131.174.8.1]) by mailhost.WI.LeidenUniv.NL (8.6.10a/FHM-1.20-M) with ESMTP id OAA23169 for ; Fri, 22 Sep 1995 14:57:25 +0200 (MET) Received: from wn3.sci.kun.nl by wn1.sci.kun.nl via wn3.sci.kun.nl [131.174.80.3] with ESMTP id OAA22551 (8.6.10/2.13); Fri, 22 Sep 1995 14:57:11 +0200 From: Peter Herweijer Received: by wn3.sci.kun.nl id OAA04309 (8.6.10/2.1); Fri, 22 Sep 1995 14:57:08 +0200 Date: Fri, 22 Sep 1995 14:57:08 +0200 Message-Id: <199509221257.OAA04309@wn3.sci.kun.nl> To: clau@netcom.com, dtauritz@WI.LeidenUniv.NL, lps@rahul.NET Subject: YA ATA-2 FAQ [1/2] Status: RO Name: Yet Another Enhanced IDE/Fast-ATA/ATA-2 FAQ Version: 1.2 Archive-name: pc-hardware-faq/enhanced-IDE/part1 Posting-Frequency: Monthly (the 24th) Last-modified: 1995/09/22 URL: http://www.wi.leidenuniv.nl/ata Maintained-by: Peter Herweijer This FAQ is the work of John Wehman (jwehman@got.net) and Peter Herweijer (pieterh@sci.kun.nl). The most recent version is available by FTP from ! ftp://ftp.aimnet.com/pub/users/clau/ide_ata ! ftp://ftp.rahul.net/pub/lps/hard-disk/ya-ata.faq ! ftp://ftp.wi.leidenuniv.nl/pub/faqs ! ftp://rftm.mit.edu/pub/usenet/news.answers/pc-hardware-faq/enhanced-IDE/ and finally by WWW from ! http://www.seagate.com/techsuppt/faq/faqlist.html ! http://www.wi.leidenuniv.nl/ata You can also get it by e-mail from pieterh@sci.kun.nl by sending message with "ATA-2 FAQ please" in the Subject: header. The body of the message will be ignored. Anything fancy will probably break the mail server and cause it to send you an uuencoded coredump :^) DISCLAIMER. The information in this FAQ comes without any warranty. The authors or distributor will not accept responsibility for any damage incurred directly or indirectly through use of the information contained in this FAQ. COPYRIGHT. This document is copyright (c) John Wehman and Peter Herweijer. You are free to distribute it by electronic means and make as many copies as you want on electronic or magnetic media, convert it to a different format, and embed control sequences, as long as the text of this document remains unmodified, with copyright notices intact. Splitting up this document is allowed on the condition that the resultant parts are presented as a recognizable whole that makes up the full, unmodified text. You are allowed to make paper copies of this document for personal use; however, distributing paper copies is prohibited without the authors' prior permission. THANKS. To everyone on comp.sys.ibm.pc.hardware.storage for encouragement and feedback, especially those who took the time to write down their comments in some detail. To Hale Landis in particular: without his input the FAQ would have been considerably less accurate on a number of key points. TODO. !* Move to SGML so that you can finally get HTML and TeX/PS versions of ! this FAQ as well as plain ASCII, and so that I can more easily add ! references to specific question numbers. !* Add more details about Win95, also in the tech section. !* Reorganize the FAQ for easier reference. !* Keep the doc references in the tech section up to date. !* Find out how I can let the FAQ show up on people's newsreaders in ! extra large pink on neon green flashing letters. !* Thousands of other improvements. ! INTRODUCTION 1.0 What is EIDE? What is Fast-ATA? 1.1 What is ATA/IDE? 1.2 What is ATA-2? 1.3 What is ATA-3? 1.4 What is ATA-PI? 1.5 What is an Enhanced BIOS? 1.6 What is a secondary port? PRACTICALITIES 2.1 What are the main features of EIDE and Fast-ATA? 2.2 What should I look for in an ATA-2 (Fast-ATA, EIDE) interface? 2.3 Is my BIOS Enhanced? How can I recognize this? 2.4 Are old IDE drives compatible with ATA-2 (EIDE, Fast-ATA) interfaces? 2.5 I have a 50MHz VLB system. Is it compatible with ATA-2 interfaces? 2.6 Can ATA-2 and ATAPI (CD-ROM, tape) drives be used with my old interface? 2.7 Do I need a BIOS update to connect an ATAPI (IDE) CD-ROM (or tape)? 2.8 Can large drives be used with my old BIOS? 2.9 I need an Enhanced BIOS to acces >504MB. How do I get one? 2.10 I have software to break the 504MB barrier. Should I use it? 2.11 Can I use a large harddisk with operating systems other than DOS? 2.12 I heard that Win95 provides supports for large IDE disks. 2.13 Does support ATAPI (IDE) CD-ROMs? 2.14 What should I use: Normal, LBA or Large? 2.15 Which drive/device should be Slave? 2.16 I need a PCI ATA-2 interface that uses only one slot. 2.17 Will adding an 'EIDE' interface help my drives' performance? 2.18 Why isn't my drive as fast as it's advertised to be? 2.19 Why is my new EIDE interface no faster than my old VLB one? 2.20 A guy on the net has the same drive and he gets 16MB/s! 2.21 Are those rumours about buggy interfaces true? 2.22 I need a longer IDE cable; how long can I make it? 2.23 I can enable write caching on my harddisk. Should I? 2.24 Can I safely change the BIOS' xlation mode (None, LBA, Large)? 2.25 Can I safely move my harddisk between computers? 2.26 I have problems with my Award 4.50G BIOS and large drives. 2.27 Can my drive do 32-bit access? 2.28 Help! I have OnTrack Disk Manager installed and now... 2.29 Help! Windows 32-bit disk access doesn't work anymore! 2.30 Help! Windows for Workgroups' 32-bit file access fails! 2.31 Help! Win95 indicates my drive uses compatibility mode! 2.32 The user's net.resource guide 2.32.1 The user's net.resource guide: I/O card drivers 2.32.2 The user's net.resource guide: hardware manufacturers 2.32.3 The user's net.resource guide: software & BIOS houses TECHNICALITIES 3.1.1 How does ATA(-2) work? 3.1.2 What are PIO modes? 3.1.3 What are DMA modes? 3.1.4 How are the Task File and data I/O ports assigned? 3.1.5 What does an ATA-2 interface do? 3.1.6 What is Block mode? 3.1.7 What is LBA? 3.2.1 How does ATAPI differ from, and coexist with, ATA(-2)? 3.2.2 What's so special the secondary port? 3.3.1 How does translation work? 3.3.2 I'd like to know how translation works in detail. 3.3.3 What is in the Enhanced Disk Parameter Table? 3.3.4 What are the issues concerning OnTrack's Disk Manager? 3.3.5 How many types of translating/Enhanced BIOSes are there? 3.4 How does Windows' 32-bit disk access work? 3.5.1 The hacker's documentation guide 3.5.2 The hacker's net.resource guide - Introduction - The aim of this introduction is to make you familiar with the most important buzzwords used in this FAQ and to provide a first overview of the issues involved. Please glance through it before reading the rest of this document. 1.0 What is EIDE? What is Fast-ATA? Enhanced IDE (EIDE) is a marketing program from Western Digital consisting of a software part--an Enhanced BIOS specification which breaks the 504MB barrier--and a hardware part that has been derived from the ATA-2 (hard drives) and ATA-PI (tapes, CD-ROMs) standards. Fast-ATA is a similar Seagate marketing program, endorsed by Quantum, that limits itself to ATA-2 (hard drives) only. If you're unfamiliar with these terms, read on :^) 1.1 What is ATA/IDE? ATA (AT Attachment) and IDE (Integrated Drive Electronics - or numerous other interpretations) are one and the same thing: a disk drive implementation designed to integrate the controller onto the drive itself, thereby reducing interface costs, and making firmware implementations easier. This low cost/easy integration created a boom in the disk drive industry, as PC integrators readily ate up the low-cost alternative. Since the late 80's, ATA (as it is properly called), has become the drive of choice for the cost inhibited buyer. 1.2 What is ATA-2? ATA-2 is a compatible extension of ATA (IDE). The most important additions are performance enhancing features such as fast PIO and DMA modes. Another important novelty is the souped-up Identify Drive command allowing a drive to tell the software exactly what its characteristics are; this is essential for both Plug'n'Play and compatibility with future revisions of the standard. While there is also a new way of addressing sectors on the harddisk (LBA), this is merely a simplification. Contrary to common myth LBA has nothing to do with breaking the famous 504MB (528MB) barrier. In fact, even in the old ATA (aka IDE) standard the theoretical size limit is well over 100GB. 1.3 What is ATA-3? Oh, help, don't ask. The first draft is out but it's a moving target ! at this stage. New features include security. Faster modes, of course, ! are also in the works: DMA mode 3 will be in the 20-32MB/s range. ! There will in all likelihood never be a PIO mode 5. Don't expect this ! to hit the stores tomorrow. 1.4 What is ATA-PI? ATA Packet Interface is a standard (draft) designed for devices such as CD-ROMs and tape drives that plug into an ordinary ATA (IDE) port. The principal advantage of ATAPI hardware is that it's cheap and works ! on on every PC with an IDE adapter. For CD-ROMs, it has a somewhat ! lower CPU usage compared to proprietary adapters but there's no ! performance gain otherwise. For tape drives, ATAPI has potential for ! superior performance and reliability compared to the popular QIC117 ! "floppy" tape devices. While ATAPI CD-ROMs use the harddisk interface, this does not mean that they look like an ordinary harddisk; to the contrary, from a software point of view they are a completely different kind of animal. They actually most closely resemble a SCSI device. This means that intelligent (e.g. caching) controllers that are not ATAPI aware will NOT work with these devices. This also means that, at present, you cannot boot from an ATAPI CD-ROM and you still must load a driver to use it under DOS or Windows. You can expect native ATAPI support in most new operating systems, though, and the first ATAPI-aware BIOS that will even allow booting from an ATAPI CD-ROM has already been introduced. 1.5 What is an Enhanced BIOS? An Enhanced BIOS is a BIOS that makes it possible to use harddisks exceeding the (in)famous 504MB (528 million bytes) barrier with DOS/Windows. The origin of this limit is the disk geometry (cylinders, heads, sectors) supported by the *combination* of an IDE drive and the BIOS' software interface. Both IDE and the BIOS are capable of supporting huge disks, but their combined limitations conspire to restrict the useful capacity to 504MB. An Enhanced BIOS circumvents this by using a different geometry when talking to the drive than when talking to the software. What happens in between is called 'translation'. For example, if your drive has 1500 cylinders and 16 heads, a translating BIOS will make programs think that the drive has 750 cylinders and 32 heads. Unfortunately there are several flavors of translating BIOSes. The de facto standard is the Microsoft/IBM 'INT 13 Extensions' document; Phoenix has presented a superset of this in their Enhanced BIOS specification. Phoenix, AMI and Award BIOSes are based on this. Another popular flavor, which is flawed and lacks vital features found in the MS/IBM and Phoenix standards, is that of the Western Digital Enhanced IDE Implementation Guide. However, the Phoenix EBIOS has broader support in the industry and is the more future-proof variant: apart from the translation, the Phoenix Enhanced BIOS specification has room for expansion beyond four ATA devices and adds important new data structures and calls to the INT13 (software) interface. 1.6 What is a secondary port? From the early days of the IBM PC there has been the possibility of connecting a 'secondary' harddisk interface; unfortunately, there has hardly been any software support up to now. There is hardly anything special about a secondary interface; it just uses a different interrupt and I/O addresses to avoid clashes with the ordinary (primary) interface. A secondary interface allows you to connect another ribbon cable with two more ATA devices (harddisk, ATAPI CD-ROM or ATAPI tape) for a total of four. The secondary port is enjoying a renaissance because the advent of ATAPI devices (CD-ROM, tape) has made four device support an absolute ! necessity. You can find the addresses and interrupts used by the ! secondary port in the tech section. - Practicalities - If you're looking for the answer to a specific question as opposed to a primer in storage technology, try this. 2.1 What are the main features of EIDE and Fast-ATA? The fast transfer modes (PIO modes 1-4 and DMA mode 0-2) are the cornerstone of Fast-ATA and EIDE. Both Fast-ATA and EIDE are marketing terms contrived by three different disk drive manufacturers. Fast-ATA is a term coined by Seagate, and endorsed by Seagate and Quantum; EIDE is coined and endorsed by Western Digital. EIDE supports these fast transfer modes, along with: * LBA mode (explained in the tech section) * Four devices on the ATA controller (secondary port) * Translation: larger than 1024 cylinder limit (WD EBIOS) * Tape Backup and CD ROM devices on the ATA controller (ATAPI) Fast-ATA and Fast-ATA-2 also support these modes, along with: * Multiple Read/Write commands * LBA mode The difference between the two schemes is mainly in the scope of EIDE. This specification encompasses many facets of drive/device technology which haven't been fully ironed out yet. With EIDE, many things can be called Enhanced, and in practice hardware is tagged EIDE even if it doesn't support all of EIDE's features. This can make for extremely confusing purchases. For that reason, this FAQ will avoid the term EIDE whenever possible, talking about its component parts (ATA-2, ATAPI, etc) instead. This hopefully allows you to get a better picture of exactly *what* 'EIDE' features you need. Another potentially confusing matter is Fast-ATA-2. The latter embraces PIO mode 4 and DMA mode 2 (16MB/s), while vanilla Fast-ATA only uses PIO mode 3 (11MB/s) and DMA mode 1 (13MB/s). Both fully comply with the ATA-2 standard, so Fast-ATA-2 should be read as [Fast-ATA]-2 rather than Fast-[ATA-2]. 2.2 What should I look for in an ATA-2 (Fast-ATA, EIDE) interface? There are a number of recent additions to PC storage technology which can play a role in purchasing a new interface. Some features, however, may already be present on your system or may be unimportant to you. The least an ATA-2 interface should provide is PIO mode 3 transfers for drives that support it. It should also provide proper support for slower PIO modes (0, 1 and 2) to ensure optimal compatibility with older drives. The "DMA" modes found on some cards often have little to do with direct memory access, unfortunately, and are of questionable merit. Other advanced features like prefetch buffers are also exceedingly rare. Since ATAPI CD-ROMs and tapestreamers are quickly becoming very popular in the low-end market, a secondary (ATA) port, which allows you to connect a total of four ATA devices, is hardly a luxury. Note that a few modern soundcards provide a secondary ATA interface instead of the traditional proprietary CD-ROM connectors; make sure it can be disabled or buy a single-ported interface. You will want an on-card BIOS too if your mainboard BIOS doesn't support translation or if it has only buggy or outdated support. The BIOS will override the mainboard BIOS where harddisks are concerned. It should preferably conform to the Phoenix Enhanced BIOS specification and build a proper Enhanced Disk Parameter Table (EDPT) when necessary. It is likely that substandard BIOSes will cause trouble with future translation- and EDPT-aware applications, even if they appear to work fine now. A BIOS ROM will, just like a mainboard with integrated EIDE, often have the added advantage that you don't need separate DOS drivers. The BIOS on an interface will occupy 16k of UMB space, though, and you will still need drivers for every other operating system you use. Drivers! Without well-designed drivers most interfaces could as well be an old-fashioned ISA card for all the good they'll do. Even if the card has a BIOS, which usually removes the need for a driver under DOS, you will still need drivers for other operating systems, including Windows and Win95. Too many drivers are unstable. ! NOTE that many popular "EIDE" interfaces to date are slightly to very ! buggy. This includes the expected problems like noncompliance with ! ATA-2, but also obscure things like the use a single buffer for both ! primary and secondary channel, which may cause data corruption under ! very specific circumstances. It can't hurt to track a few newsgroups ! for hands-on experiences. A group to watch, beside the hardware ! groups, is comp.os.os2.bugs. 2.3 Is my BIOS Enhanced? How can I recognize this? Good question. Unfortunately, I know no easy answer. The mere ability to specify more than 1,024 cylinders in the BIOS setup is _not_ conclusive. In your BIOS setup, drive related settings like "LBA", "ECHS" or even something silly like "Large" are telltale signs of a BIOS with translation support. A copyright before 1994, on the other hand, ! reduces your chances to something close to zero :^( ! ! - AMI BIOSes dated 7-25-94 and later and support translation. The ! date is embedded in the long number displayed at the bottom of ! the screen on bootup. It must be 072594 or later to support LBA. ! ! 40-0100-00101111-111192-486-ABC-F (111192 will not support LBA) ! 50-0100-001292-00101111-072594-ABCDEF-F (072594 will support LBA) ! ! - Award seems to call all its BIOSes 4.50G :^) Some have translation ! support, some don't, some have buggy support (see elswhere in ! this section for more information). ! - Phoenix BIOS v4.03 and later are reported to support translation. ! Some revisions of Phoenix v4.03 may not support it, though, ! depending on the computer or system board manufacturer. ! ! - I had one report that MR BIOS incorporated CHS translation as ! early as v1.40 (1992!). Western Digital has a utility available by ftp that examines the Enhanced Disk Parameter Table (EDPT), if present. If it finds one on your system, your BIOS has all the bells and whistles (ftp://ftp.wdc.com/drivers/hdutil/chkbios.com). Beware that BIOSes conforming to the WD Enhanced BIOS specification won't build an EDPT unless LBA is enabled. Beware also that with a WD EBIOS it is highly unsafe to enable LBA on a disk that already contains data. This is due to a flaw in the specification. If you're desperate enough, you can also find out by simply trying to enter more than 1024 cylinders and using, for example, MSD to find out if the BIOS mangles the geometry or not, but we don't take responsibility for what may happen to your harddisk. Take care not to write even a single byte to it! 2.4 Are old IDE drives compatible with ATA-2 (EIDE, Fast-ATA) interfaces? Yes, this should work fine. To be used in an advanced mode, the drive has to support the ability to transfer data at the fast rate. Also, the controller needs to be able to run at fast mode speed. Older drives can work with ATA-2 interfaces, provided these interfaces have the intelligence to query the drive as to its maximum transfer rate. There is a drive command (Identify Drive) that gets a sector's worth of data which holds all types of drive information, including the data transfer rates. The controller MUST be able to identify this for the drive to work properly. Blind PIO Mode 3 (programmed to fast mode without querying the drive) in an older drive that can't support it will end up corrupting data, hanging the drive, and just making a mess of things. But, most controllers out there have some intelligence built in. If you intend to put an older drive on the same cable as an ATA-2 drive, you may want to verify that your interface is capable of using independent timing for master and slave drive. Otherwise, your old drive might end up holding back your newer one. 2.5 I have a 50MHz VLB system. Is it compatible with ATA-2 interfaces? It should be, but there are problematic cases. ! It has been observed that some controllers will base their I/O cycle ! times on the bus clock of the computer. This means that with a 50MHz ! bus, the cycle time will be faster than with a 33MHz bus. This could ! lead to undesirable results if these cycle times are faster than the ! drive can handle. Make sure your controller supports multiple bus ! speeds in the software setup, and program it correctly. ! 2.6 Can ATA-2 and ATAPI (CD-ROM, tape) drives be used with my old interface? ! ! Fast-ATA, EIDE and ATAPI drives can be used without fear on regular ! ISA IDE controllers. The thing about advanced modes is that the drive ! is ready for the data in the fastest mode; the slower the controller, ! the easier it is on the drive. All these devices were designed to be ! compatible with ordinary IDE interfaces. ! Be sure to read the next questions too. ! 2.7 Do I need a BIOS update to connect an ATAPI (IDE) CD-ROM (or tape)? ! ! No. These devices ship with a driver that provides complete support. ! The BIOS doesn't need to support it and usually doesn't even know it's ! there. ! 2.8 Can large drives be used with my old BIOS? Yes, in principle, but there is the small matter of the 504MB barrier. If the new drive exceeds this capacity, you should ensure you have an ! Enhanced BIOS if you want to use more than 504MB with DOS, Windows or ! Win95. It is important to note that this is a software only issue: you ! do _not_ need a special interface to support large drives. BE WARNED that some older BIOSes will incorrectly handle drives with more than 1024 cylinders. Instead of truncating the number of cylinders to 1024, they use the cylinder count modulo 1024. The solution is to specify 1024 cylinders in the BIOS setup. This becomes a real problem with BIOSes that don't allow you to enter the drive parameters manually. The 1991-vintage PS/2 models 35sx and 40sx do this, as do all of the ValuePoint models up to, but not including, the 1994 ValuePoint Performance series. With these machines, you should verify that the drive has a way to fake having no more than 1024 cylinders (Western Digital has a utility for their 540MB drive, and many Maxtor drives have a jumper). Note that some operating systems, such as Linux and OS/2, allow you to override the BIOS' drive geometry information. 2.9 I need an Enhanced BIOS to acces >504MB. How do I get one? The options are: a new mainboard BIOS, add-on BIOS, or software. To upgrade your mainboard BIOS, either by a newer version of your current BIOS or by a custom made BIOS from firms such as Microid Research (MR BIOS), is probably the best option. It may or may not be more effective to replace the entire mainboard and get all the latest bells and whistles for $100 more. The next option is to purchase an add-on BIOS that effectively replaces the harddisk portion of your mainboard BIOS. Most BIOSes on ATA-2 interfaces, if they have a BIOS at all, also do this, so that may be a nice way to go if your present interface isn't up to snuff. Either way, you will have to repartition and reformat the (large) harddisk. A final option is to use a software solution. Be sure to read the section about this below. 2.10 I have software to break the 504MB barrier. Should I use it? This is the most convenient option for some, but there are caveats. The software, while it is known by all kinds of exotic names depending on who licensed it, is usually a version of either MicroHouse's EZ-Drive or OnTrack's Disk Manager. Disk Manager, when used on the boot drive, has to resort to some trickery in order to be loaded very early during the boot process (which is necessary for technical reasons). This is accomplished by modifying the Master Boot Record (MBR) and storing a Dynamic Drive Overlay (DDO) on the very first disk track. EZ-Drive works in a similar way. ! An annoying side effect of using a software solution is that operating ! system installations, which often overwrite the MBR, will render the ! contents of your harddisk inaccessible. You will need to restore the ! MBR from the installation floppy to regain access to your partitions. ! ! Moreover, with at least some versions of this software, the partitions ! it creates are completely incompatible with, and unreadable by, ! everything else. Generic disk-related device drivers fail with even if they work with all other translation schemes. Important examples are (E)IDE interface drivers; remember that without these drivers an interface will in general be much slower. You'll need drivers that are specifically aware of the translation software you use. Also, many operating systems other than DOS will not be able to access or use the drive, at least not 'out of the box'. Disk fixing utilities may fail to work if the partition table or the DDO/XBIOS overlay is damaged. ! OnTrack's (ttp://www.ontrack.com, tech@ontrack.com, ! sales@ontrack.com) latest version of DiskManager (v7) is a vast ! improvement on v6. It allows multiple operating systems and is ! compatible with most interfaces and drivers, including those for ATAPI ! CD-ROMs. For older versions, IBM and Microsoft have fixes for OS/2 (in ! the Bonus Pack) and NT (Service Pack 2). Win95 should support Disk ! Manager and EZDrive out of the box (see Microsoft KnowledgeBase ! article Q126855). More about Disk Manager in section 3. We lack ! details about EZDrive. 2.11 Can I use a large harddisk with operating systems other than DOS? ! This is often less of a problem than with DOS, Windows and Win95, but ! take care since some OSs don't understand translation. With operating systems such as NetWare, Unix, Win/NT and OS/2, the only thing you need to use large ATA disks is a BIOS that allows specification of more than 1024 cylinders in the drive type setup. Since these OSs use the BIOS only when booting, the only consequence of not having an Enhanced BIOS is that boot managers, boot partitions etcetera have to reside below cylinder 1024. Once running, these operating systems use their own software to ! control the disks (Win95 also does this, but has a special position; ! see below). That way, they are not subject to the BIOS' restrictions ! such as the capacity limit. Unfortunately, this also means that if you ! have a translating EBIOS or software driver, the OS has to be aware of ! the translation scheme used, or conflicts will arise between the ! operating system and DOS/Win/Win95. If you can set up partitions so ! that all DOS and boot partitions reside below the first 1024 cylinders ! (504MB), you can avoid translation altogether and all the hassles with ! it. ! ! Older operating systems don't understand translation at all. Newer ! ones (OS/2 3.x, Linux 1.2, more?) will handle standard translation ! schemes out of the box, but not always those employed by some software ! drivers (EZDrive, Disk Manager v6.0 or older). In the case of DM 6, ! fixes or updates are available for some operating systems (see above). ! ! Novell Netware has a driver IDE.DSK version 3.0 dated September 2, ! 1994. This version of the driver uses the Get Current Parameters ATA ! command and ignores the BIOS parameters. This means that Novell now ! works with Big IDE drives. ! 2.12 I heard that Win95 provides supports for large IDE disks. ! ! True, but it doesn't necessarily mean you can actually use these ! disks in all cases. ! ! Despite a large number of significant changes, in its way of handling ! harddisks Win95 largely resembles Windows for Workgroups. Just like ! OS/2, Linux and other operating systems, Win95 uses 32-bit protected ! mode drivers for the harddisks (unless it's using compatibility mode), ! and is happy to handle harddrives of respectable size (well over ! 100GB). However, unlike OS/2 and Linux, and like WinfWg, Win95 boots ! from the same old DOS we all love to hate. Even once Win95 has booted, ! DOS isn't gone. Win95 always keeps it behind the scenes and uses it ! to run devices in compatibility mode. In "safe mode", important for ! troubleshooting, Win95 even completely relies on DOS. ! ! What all of this implies is that even though Win95's protected-mode ! disk driver may support gargantuan drives, it will refuse change the ! setup it inherits from DOS in order to retain compatibility with the ! latter. If you can only get at the first 504MB of your drive in DOS, ! it will be the same in Win95. You will still need one of the usual ! >504MB solutions mentioned elsewhere in this FAQ. For details, see ! also Microsoft KnowledgeBase article Q126855, "Windows 95 Support for ! Large IDE Hard Disks". ! ! There's still hope, however, for drives that don't have any BIOS ! support at all (e.g. on the secondary channel, or drives that are set ! to "Not installed" in the BIOS). The FDISK that comes with Win95 may ! not be up to it, though. Watch this space for more details. ! 2.13 Does support ATAPI (IDE) CD-ROMs? ! ! The current versions of most operating systems support ATAPI CD-ROMs. ! That includes OS/2 3.0, Linux 1.2, and Win95. ! ! The problem is that hardware manufacturers have started designing ! these CD-ROMs while the ATAPI standard was still evolving, so that ! there are now a couple of revisions implemented in the real world. ! Moreover, the complexity and newness of ATAPI means that there are ! slight variations even among implementations of the same revision. ! Writing an OS ATAPI driver that works with all CD-ROMs, therefore, is ! a daunting task and not all have succeeded equally well. So although ! these OSs all support ATAPI, they do not work with all ATAPI ! equipment! ! ! See Microsoft KnowledgeBase Q131499, "CD-ROM Drives Requiring ! Real-Mode Drivers", for more details on Win95 support. 2.14 What should I use: Normal, LBA or Large? 'Normal' causes the BIOS to behave like an old fashioned one without translation. Use this if your drive doesn't need it (ie. has fewer than 1024 cylinders) or if you want to use the drive with a non-DOS operating system that doesn't understand translation. 'Large' tells the BIOS to use CHS translation. It uses a different geometry (cylinders/heads/sectors) when talking to the drive than when talking to the BIOS. This type of translation works with all drives. 'LBA' differs from 'Large' in that it uses so-called LBA addressing to access the harddisk. The advantage of LBA is that it theoretically is a little faster. The disadvantages are that not all drives support it, not even all large ones, and it sometimes turns out to be slower, depending on the drive. WARNING! The BIOS may change the (translated) geometry if you change from Normal or Large to LBA. The same thing may happen if you transfer a disk that has been formatted on an old, non-LBA computer to a new one that uses LBA. This HAS destroyed data. Section 3 tells more about the differences between these three. 2.15 Which drive/device should be Slave? ! For two harddrives or two ATAPI devices (CD-ROM, tape), it shouldn't ! matter which is which, although an older harddrive may not work in all ! configurations. If you need to put a harddisk and an ATAPI device on ! the same cable, though, the harddisk _must_ be the master. ! ! Also, remember that you should never have a slave without a master ! present. Take care, because many ATAPI devices come preconfigured as ! slave. 2.16 I need a PCI ATA-2 interface that uses only one slot. There is a problem with PCI and multi-I/O or dual-ported IDE interfaces. These interfaces need two or more (predetermined) interrupts, which may not be possible with your PCI slots. The usual workarounds are either a tiny "paddle" board that plugs into an ISA slot, or integration of I/O functions on the mainboard. Some vendors use single-slot PCI interfaces that rely on a proprietary extension of the PCI bus. This is obviously not portable; you often can't even move the card to a different slot in the same machine. This is not so much a weakness in the design of PCI, but a conflict between PCI's plug'n'play philosophy and the requirement that these cards be fully compatible with old cards. 2.17 Will adding an 'EIDE' interface help my drives' performance? A new interface may or may not help; it is possible to make a rough prediction if a better interface would really work. Hardware vendors and marketing people would love to see everyone rush out and buy the latest generation of "EIDE" adapters. To achieve this noble goal they tend to juggle with too-good-to-be-true performance figures. The relation between this advertising hype and the real world is shaky at best. The main point to remember is: a slow drive is a slow drive no matter how good the interface. If the speed at which the drive physically transfer the data to/from the media is the limiting factor in performance, and it often is, the only way to make things go significantly faster is to purchase a better drive. Note that the transfer modes supported by modern drives (those 11MB/s or larger figures) have little to do with their performance. In addition, an 'ordinary' VLB interface may already offer respectable bandwidth---the fastest ATA transfer mode is theoretically 8.3 MB/s, which is more than any ATA-2 drive can sustain. An ISA interface rarely exceeds 2.5MB/s, which is a bit cramped for modern drives. How to determine if the drive is the bottleneck? You can get a rough idea by using two different benchmarks. The first benchmark should be a decent one that really tests the throughput from the drive platter to memory, such as Norton SI or QBench. For the second you take a 'benchmark' that merely moves data between the processor and the drive's buffer cache without exercising the media at all. A popular example that works well on drives with a buffer cache of 64k or more is Coretest. This second result, while worthless as a disk benchmark, is a rough indication of the interface bandwidth. Often you'll find that the second figure exceeds the first by a considerable margin (over a factor two). This means that the properties of the drive itself are the bottleneck, and improving the interface speed any further won't really help. The only thing that may improve performance somewhat is using block mode (using either a BIOS option or a driver). Only if the drive throughput starts to approach the interface bandwidth will you have a fair chance that a new interface will have a large impact on performance, _provided_ the drive supports the faster modes. Be sure to read the following questions to get a more complete picture. 2.18 Why isn't my drive as fast as it's advertised to be? Good question. The basic answer is that the advertised modes are *theoretical* transfer rates. This means that for transfers to or from the buffer cache, the data will be transferred across the bus at n Bytes in 1 second. Realistically, however, drives do more than just give data to the host out of cache. For each sector transferred to the host, it needs to get one from the media. This reduces the overall "bandwidth", or the total drive's clock cycles dedicated to these tasks. Also, there is internal controller processing, table updates, and positioning information that has to be taken into consideration. This all reduces the throughput of the data cache to the bus. On top of that, depending on the benchmark used to determine the "throughput", the rate can vary from 1MB/s to 9MB/s and upwards, all on the same drive. Plus, system configuration (MHz CPU, RAM, Smartdrv (if DOS), L1 cache) make a difference as well. Finally, different areas on the same disk can exhibit as much as a factor two difference in transfer rate. Bottom line is, whatever benchmark you use, you will not "see" the advertised transfer rate. The real test is how well it improves *your* day to day applications. The rest is just fluff. 2.19 Why is my new EIDE interface no faster than my old VLB one? There are several reasons why it is possible that an ATA-2 interface is no faster than a local bus ATA one even if the drivers are installed and everything works properly. The first, and most important, is that the bandwidth of the fastest ATA mode, 8.3MB/s, exceeds the real world transfer rate of most drives on the market today by a considerable margin. If this is the case for your drive, increasing the interface bandwidth beyond this will have no noticeable effect. A further possibility is that your drive does not support the ATA-2 transfer modes at all. In that case, an ATA-2 interface may improve performance relative to an old-fashioned ISA bus interface, but it will be no faster than a good local bus ATA interface. Finally, if the ATA-2 interface does not support separate timing for master and slave drives, putting an ordinary ATA drive on the same cable as an ATA-2 drive will reduce the interface speed to that of the lowest common denominator. 2.20 A guy on the net has the same drive and he gets 16MB/s! "Usenet is like a herd of performing elephants with diarrhea-- massive, difficult to redirect, awe-inspiring, entertaining, and a source of mind-boggling amounts of excrement when you least expect it." -- Gene Spafford (spaf@cs.purdue.edu), 1992 2.21 Are those rumours about buggy interfaces true? ! ! Very true, unfortunately. ! ! This FAQ doesn't really deal with specific interfaces, but recently ! two very popular interface chips have been shown to contain bugs too ! serious to ignore: the CMD640x, a dual-channel PCI to EIDE interface ! used on many mainboards (Intel!) and interface boards, has a number of ! data-corrupting bugs you need to be aware of. The PC-Tech RZ-1000, ! used on AT&T, Dell, Gateway, IBM and Intel boards, also has two ! data-corrupting bugs. In all cases, the corruption occurs only in ! specific software environments and is very subtle; you can go on ! working for months without suspecting anything more than buggy ! software. The damage can be immense. ! ! For the details, look at Roedy Green's EIDE flaws FAQ posted to the ! comp.os.os2.bugs newsgroup. This FAQ is definitely of general ! interest; read it even if you wouldn't touch OS/2 with a ten foot ! pole. You may also find links on http://www.powerquest.com. Working on ! an affected machine without informing yourself amounts to playing ! Russian roulette with your data. ! 2.22 I need a longer IDE cable; how long can I make it? ! ! Less than 18 inches. In some cases, the limit is no more than 7 ! inches. ! ! The cable is a pretty weak link in the whole ATA interface. For the ! fast transfer speeds used in "EIDE" systems, there aren't enough ! ground signals; the cable is unterminated and unshielded. Noise is a ! real problem. For those reasons, you should take the 18" limit ! specified by the ATA(-2) standard pretty seriously if you want to ! avoid data corruption and system hangs. _This is not mere theory_. ! ! Even worse, some dual-channel "EIDE" interfaces such as CMD640 based ! ones have a peculiar design in which only a single buffer is used for ! both cables. Most signals on the cables are directly connected with ! each other: this means that electrically, the cable lengths ADD UP. ! Take into account that the traces on the circuit board are often a ! couple of inches long as well and you're facing a maximum cable length ! of roughly 7" per cable if you want to remain within spec. ! ! Disregard the above at your own peril. Noise induced problems usually ! occur sporadically, can be very hard to detect and even harder to ! track down. ! 2.23 I can enable write caching on my harddisk. Should I? Do not confuse this with Smartdrive (or whatever) lazy writes: what is meant here is altering the drive's buffer cache management algorithm. This is possible using newer versions of Drive Rocket, with hdparm under Linux, and probably other utilities too. Provided, of course, the drive supports this feature. Sometimes it can also be done using jumpers on the drive. There seem to be problems with this, if a program will issue a soft-reset (which on Intel Pentium Motherboards also issues a hardware-reset) as soon as it sees the last IRQ, which overall ends up corrupting data. Use with care, and BACKUP. 2.24 Can I safely change the BIOS' xlation mode (None, LBA, Large)? Unfortunately, no. Proceed with care. While with many BIOSes, the sectors on the disk are addressed in the same order independent of the translation mode, some use a different type of translation algorithm. The latter type of BIOS will shuffle your data as if it were a deck of cards if you alter the translation mode. Moreover, BIOSes that conform to the WD Enhanced BIOS spec may use completely dissimilar drive geometries in the software (INT13) interface depending on the translation mode, which opens up the possibility of data corruption. This is a major flaw in the WD EBIOS specification. ! In these cases, after changing the translation mode, you must ! repartition and reformat your disk. ! 2.25 Can I safely move my harddisk between computers? Transferring a partitioned and formatted harddisk between computers is potentially dangerous if they use different translation schemes (see above) INCLUDING moving disk from an old computer that doesn't support translation at all to a new one that does. This is really a little known issue. Usually everything goes smoothly, but you would NOT be the first to be caught by surprise. DO NOT ASSUME IT WON'T HAPPEN TO YOU. IT *HAS* DESTROYED DATA. 2.26 I have problems with my Award 4.50G BIOS and large drives. If your 4.50G BIOS is dated earlier than 13/12/1994, the address translation table is faulty. To access drives with more than 1024 cylinders, you cannot use address translation (Large) but *must* use ! LBA. In versions dated 13/12/1994 or later this has been fixed. Be ! warned that switching to LBA will probably force you to repartition ! and reformat your drive; do back up your data. 2.27 Can my drive do 32-bit access? There appears to be an awful lot of confusion about this subject, partly due to some unhappy terminology. In the most literal sense, no ATA(-2) drive will allow 32-bit access. Data is transferred to and from the drive over a 16 bit bus. However, many local bus interfaces are capable of combining two 16-bit words into a 32-bit doubleword when reading data from the disk, and the reverse when writing. This way, data transfer between the CPU and the interface can be done in 32-bit chunks. This is often called 32-bit access, although 32-bit host bus transfers would be a better name. With 32-bit host bus transfers, more efficient use is made of the computer's bus and CPU. On the other hand, these are seldom the bottleneck, so don't expect miracles from this feature. Windows' 32-bit disk and file access are completely unrelated issues and the subject of the following questions. 2.28 Help! I have OnTrack Disk Manager installed and now... ! OnTrack has a web site: http://www.ontrack.com. There's also a bit ! about DM in section 3. Read it. If that doesn't help, contact OnTrack ! tech support (e-mail: tech@ontrack.com). 2.29 Help! Windows 32-bit disk access doesn't work anymore! There are numerous reasons why 32BDA can fail; you will more easily be able to do something about it (or decide if you want to fix it in the first place) if you know a bit of what it does. Windows' 32-bit disk access (32BDA) is a bit of a misnomer, actually, since it has nothing to do with 32-bit data transfers. A slightly better name for it is "FastDisk". It is a feature of Windows in 386 Enhanced mode that allows one to replace the BIOS' disk routines by Windows' own routines that work in protected mode. A much better name, then, would be "protected mode controller access". For some reason Microsoft decided not to use the latter. Anyway, the main advantage of this feature is that with it, Windows can use virtual memory for its DOS sessions. Without 32-bit disk access, DOS sessions cannot be swapped out and every DOS box takes 640k of REAL memory. Because it also reduces the number of switches between virtual and protected mode Windows has to make, it gives a slight performance improvement as well, but usually nothing dramatic. If 32BDA is used together with Windows for Workgroups' 32-bit file access feature, it will eliminate these mode switches altogether (at least for many disk operations), which gives a far more interesting performance boost. Unfortunately, the standard FastDisk routines that are internal to windows, called *wdctrl, are severely limited in their capabilities. The *wdctrl software understands nothing of non-IDE hardware (e.g. SCSI), more than two harddrives, drives with more than 1024 cylinders, 32-bit host bus transfers, block transfers, or ATAPI CD-ROM drives on the primary ATA channel. If you use any of these things, 32-bit disk access won't work unless you have a *wdctrl replacement. Today, that means that 32-bit disk access won't work "out of the box" for most of us. Most interfaces that are incompatible with *wdctrl come with their own FastDisk routines (usually with a .386 extension). For the rest of you, many drive manufacturers offer replacement FastDisk software. For Western Digital you can use ftp.wdc.com (/drivers/win31.exe); for other brands their BBS is your best bet. You can also contact your vendor to find out what is available. NB. These drivers are incompatible with the Stealth feature of some versions of Quarterdeck's QEMM. Quarterdeck's fix can be found on ftp://ftp.wdc.com/drivers/hdutil/32bda.com. 2.30 Help! Windows for Workgroups' 32-bit file access fails! The idiosyncrasies of the 32-bit disk access feature with respect to disk hardware has led to the popular myth that 32-bit file access has similar problems. However, that's all it is: a myth. If 32-bit file access fails, you should first check your filesystem and the programs that use it. As little as a single open file, e.g. from a printer spooler, will cause 32BFA to fail. Oh, and put DEVICE=C:\WINDOWS\IFSHLP.SYS in your CONFIG.SYS, and make sure your SYSTEM.INI contains the correct magic incantations (vfat.386, vcache.386). If this doesn't help, read the FAQ on this topic (see the net.resource guide for details). 2.31 Help! Win95 indicates my drive uses compatibility mode! ! ! This section is under construction. ! ! The culprit usually is a DOS (real-mode) driver that loads in the ! config.sys or autoexec.bat, or an old version of EZDrive/Disk Manager ! loading from the MBR. ! 2.32 The user's net.resource guide There are a couple of related FAQs floating around on the net. Hale Landis (landis@sugs.tware.com) has a few excellent, if pretty technical, documents, posted irregularly, which he keeps on intending to revise :^) Daniel Tauritz (dtauritz@WI.LeidenUniv.NL) no longer maintains EIDE Mini-FAQ that contains a short but potentially useful list of available interfaces; it needs to be expanded and maintained---any takers? All this and more can be found on ftp://ftp.wi.leidenuniv.nl/pub/faqs http://www.wi.leidenuniv.nl/ata Don't forget the comp.sys.ibm.pc.hardware FAQ, maintained by Ralph Valentino. It can be found on comp.answers and the FAQ repository rtfm.mit.edu. It incorporates the world-famous 'Jumper FAQ' (see ftp://rtfm.mit.edu/pub/usenet/news.answers/pc-hardware-faq/part3). On the tangential subject of Windows for Workgroups' 32-bit FILE access, Mike McCormick (m.mccormick2@genie.geis.com) has a good FAQ in ! progress, posted on comp.os.ms-windows.windows.setup and many other ! groups. It can also be found on comp.answers and therefore on ! rtfm.mit.edu too. ! ! There are some excellent lists being compiled on the OS/2 groups that ! are also of general interest. Roedy Green's EIDE controller flaws FAQ ! (on comp.os.os2.bugs) deserves special mention; if you've got a CMD640 ! or RZ1000 interface chip (used on many pre-Triton Intel Pentium ! boards, for instance), you're playing Russian roulette every day if ! you don't read this. The SimTel repository, the primary mirror of which is oak.oakland.edu, contains an immense number of useful material (PD, freeware and shareware). A tiny selection, all from SimTel/msdos/diskutil: ideinf10.zip (will determine the properties of your harddisk(s)-- NOT a benchmark). 3drvs260.zip (gives support for 3 harddisks under DOS). dqwik211.zip (block mode driver). no_idle.zip (disables the auto- idle power saving feature of some harddrives). 1seagate.zip (specs for *all* Seagate harddrives). wasted14.zip (shows wasted space due to cluster size). presz111.zip (partition resizer). A more manageable selection of useful utilities, drivers and information (this FAQ :^) can be found on ! ftp://ftp.aimnet.com/pub/users/clau/ide_ata ! ftp://ftp.rahul.net/pub/lps/hard-disk Frank Pikelner (frank@cs.yorku.ca) has compiled a list of >500MB harddisk and >4x CD-ROM drive specifications. You can access it through http://www.cs.yorku.ca/People/frank/Welcome.html. If it looks weird, your browser doesn't support the TABLE tag. 2.32.1 The user's net.resource guide: I/O card drivers There's an initiative to build a depository of IDE card drivers; you can find these at ftp://ftp.funet.fi/pub/drivers/pc/disk/ide_ata 2.32.2 The user's net.resource guide: hardware manufacturers A number of disk manufacturers now have FTP and web sites; these are ! Conner ! http://www.conner.com ! IBM http://www.ibm.com http://www.pc.ibm.com (PC Company) Iomega (they don't make harddrives, but oh well...) http://www.iomega.com Maxtor http://www.maxtor.com ftp://ftp.maxtor.com All files from their BBS are on the FTP site, including biosbnch.zip, a benchmarking utility; greendrv.zip, to set the sleep mode timer on 'green' drives. ! Promise ! http://www.promise.com ! ftp://ftp.promise.com ! Quantum http://www.quantum.com No official FTP site, although drivers to use Quantum's large harddisks with a non-translating BIOS can be found in ftp://ftp.rahul.net/pub/lps/hard-disk/ide_dos.exe This is NOT an official Quantum support site and may disappear. This site contains miscellaneous storage-related programs and information too. Seagate ftp://ftp.seagate.com http://www.seagate.com This includes specifications of ALL Seagate drives, including detailed diagrams/pictures. Western Digital ftp://ftp.wdc.com http://www.wdc.com Many drivers and utilities, some of which won't work if you don't have at least one WD Caviar drive in your system. Goodies to be found: a good Windows FastDisk driver in /drivers/hdutil/win31.exe; a Windows helpfile explaining Enhanced IDE in /docs/eide.exe; a utility to examine the Enhanced DPT of your BIOS: /drivers/hdutil/chkbios.com. Pointers to sites offering software from other manufacturers would be appreciated. ! If 'your' manufacturer doesn't have a net site, you may want to check ! the harddrive spec listings to be found on ftp://ftp.ee.ualberta.ca/pub/drives http://www.ee.ualberta.ca/ftp.html 2.32.3 The user's net.resource guide: software & BIOS houses AMI ftp://american.megatrends.com IBM http://www.ibm.com http://www.pc.ibm.com (PC Company) ! ftp://ftp.pcco.ibm.com ! ! Flash BIOS upgrades for the IBM ValuePoints are in pub/valuepnt/. Microsoft ftp://ftp.microsoft.com http://www.microsoft.com General Windows and DOS updates, fixes and Microsoft Knowledge Base articles can be found on the Microsoft FTP site (ftp.microsoft.com). Unfortunately, the structure of this site can hardly be called intuitive (which, some would argue, is characteristic of Microsoft ! products in general). The WWW site allows searches in the Knowledge ! Base, which is much more useful. Novell http://www.novell.com http://www.netware.com (Netware info) OnTrack http://www.ontrack.com e-mail: tech@ontrack.com (tech support) sales@ontrack.com (sales). Phoenix http://www.ptltd.com SCO http://www.sco.com (CONTINUED IN PART 2)