Thanks go to whoever typed this DOC. It was edited for Doc Disk 9 by Sewer Rat. As usual, we take no responsibility should you totally fuck your ST up, by doing these modifications yourself. Opening capture buffer... Here's the 1 Meg upgrade directions: I have brought this over un-editted from the arpanet info-st mailing list. I TAKE NO RESPONSIBILITY FOR ITS CONTENT OR ACCURACY. I HAVE NOT TRIED THIS MODIFICATION ON MY OWN ST AS YET. I AM PASSING THIS ALONG TO THOSE WHO DO WISH TO TRY IT. FOLLOW THE DIRECTIONS AT YOUR OWN RISK. WARNING: This is a hardware modification that will void the warranty of your 520ST. If you do not have the appropriate tools or experience you have a substantial chance of ruining your 520ST. Proceed at your own risk! This modification has been in my 520ST without any problems for 6 days now. However, I have (of course) not checked with knowledgable sources at Atari to verify if this modification endangers the long term machine reliability and/or software compatibility (I suspect it may endanger their software compatibility if enough of us do it!) Tools & components needed : 16 256k * 1 RAM chips, 150 ns access time type, e. g. NEC 41256C-15 A good quality, preferrably temperature controlled soldering iron, with a minature tip (tip should be narrow enough to avoid touching 2 I. C. pins at the same time). E. g. Weller type soldering station. Good quality resin core solder (thin). Approximately 4 foot of wire-wrap wire and a good stripper for it. (you will have to route 3 wires over a sequence if I.C. pins. The easiest way to do this is to have a stripper allowing you to shift the insulation forward over the wire, solder the next point, measure new length, shifover insulatiooon, etc. until the endpoint). The "No Nik" 0.014 (dark green handle) wire wrap stripper is the best tool for this. Desoldering wick and solder suction tool. Philips type screwdriver (for opening your ST), tweezers, pliers, etc. A steady hand and self-confidence. Explaination of the modification : (Please read the rest of this document before starting. It may save you time and an 520ST!!!) The current memory inside the 520ST consists of 16 256K*1 RAM chips. Address (A0..A8) lines are common to all those chips. The Write Enable line is also common to all chips. Data (in and out) lines are of course individual. The RAS (row-address strobe) line is common to all chips. The 8 chips forming the high order byte group have one common CAS line, and the 8 forming the low order byte group have one common CAS line (CAS is used as enable for write operations, such that WriteEnable can be common to both groups). The high order group from MSB to LSB consists of U45, 44, 43, 42, 38, 34, 33, 32. The low order group of U30, 29, 28, 25, 24, 28, 27, 26. Note that all chips are adjacent, though the numbering has gaps. RAS0, CAS0H, and CAS0L are supplied from U1 pin 8,6 and 7 respectively (The 0 indicates bank 0) Bank 1 that you are going to build in will be "piggy-backed" on top of the current chips, where all pins of the new chips EXCEPT RAS (pin 4) and CAS (pin 15) are soldered to the old chips equivalent pins. Thus they will end up sharing addresses, data, Write Enable and power with the existing chips. All ras pins of the new chips are wired together and will be supplied with the "RAS1" signal generated on pin 18 of u15 (memory controller, marked 3H-2119C or so). The CAS pins of the 8 new high order byte chips (on top of U45..U32) are wired together and supplied from the "CAS1H" signal generated on pin 22 of U15. Analogously, the CAS pins of the new U30 to U16 are wired together and supplied with "CAS1L" from pin 21 of U15. How to go about it:- Step 1: Open up your 520ST, pull off the keyboard connector and remove the main circuit card from its top and bottom shielding. Make sure to remember which screws go where and note the keyboard connector orientation. Step 2: Desolder all of the capacitors adjacent to the existing RAM chips. (DO NOT SKIP THIS STEP. You'll lose time if you do, and worse, the modification will no be reliable since you can't solder pins obstructed by the capacitors reliably (if at all)). To desolder them, I found it easiest to heat the island on the non component side, and bend the wires straight. After doing that or each capacitor, turn over to the component side and heat the islands wile pulling the capacitor out with the tweezers. Step 3: Open up the holes of all the desoldered capacitors, using a combiation of de-soldering wick and suction tool. Do this from the non component side. If certain holes are difficult to open up, you may want to use a wood splinter. (push it through while heating). Be carefull to remove all solder debris!! THE REASON for opening the holes NOW is that they will be less accessible once you've done the other steps! Patience is a virtue. (NOTE: Step 2 & 3 are the only ones that may damage your ST PC board. Be sure not to use excessive force while pullling out the capacitors. If you damage your PC board anyway, cure the problem now and not later). Step 4: In this step we will piggyback the new RAM's on top of the old oes. Be sure to connect all pins except pin 4 (RAS) and 15 (CAS). The best way to go about this is to do chip by chip. First, bend the pins of the new RAM's such that they are perpendicular to the package (instead of having slightly spread "cowboy legs"). Use pliers to bend pin 4 and 15 such that it comes out of the I.C. package horizontal, and cut off the excess length of pins 4 and 15 (I mean part of the pin, you still need to be able to solder to it!). Make sure that the new RAM fits snnugly on top of the old one (in the same orientation!!!), without intervening space and with the new pins touching the old ones. Now solder each pin (except the non-touching 4 and 15) to the other RAM's. The best way to do this with the least chance of damage is to touch both the new RAM's pin and the old RAM's pin. Heat them both for a second and add A LITTLE solder then. Wait till the solder flows. After each I.C., check all pins carefully to assure a good connection. (use a magnifying glass) NOTE: This step is crucial for the long term reliability of the memy extension. AAA badly soldered joint may show up later as sporadic memory errors. TAKE YOUR TIME. (NOTE: until step 6 is finished, do no in any way apply power to your ST. This intermediate state of affairs will damage your memory chips!!) Step 5: Remount all the desoldered capacitors. Bend the pins like they were before resoldering, suchthat they will not touch the lower shielding. Solder from the non component side. Step 6: In this step you will route the 3 wires mentioned earlier. The first wire connects pin 4 (RAS) of all the new RAM's to pin 18 of U15. The second wire connects pin 15 (CAS) of the new U45 to U32 to 22 (CAS1H) of U15. The third wire connects pin 15 (CAS) of the new U30 to U16 to pin 21 of U15. The best way to do this is to use the stripper to remove 5 inches of insulation. Solder the first IC pin to the end of the blank wire, measure the distance to the next pin in sequence and shift over that amount of insulation. Continue in this fashion until all the pins in sequence are done. Work from U45 to the left, soldering directly to the leftover pins on the new chips. Make sure that no wire or solder sticks out above the the top plane of the new chips, since they will almost touch the top shielding! Route he wires through the PC board hole below and to the left of U15 to connect to U15 on the non component side. Step 7: Sit back. Use Brain. Do you feel confident about the quality of your work? No mistakes? Check evrything once again if you are but a little uncertain. Applying power with errors might make your ST into a decorative, nonfunctional piece of art. OK. Either rebuild your ST into its shielding and cabinet, or put it onto a surface clear of wires and solder remians and connect it to monitor, disk and supply. Boot it. It it boots, you're probably there. Test if the new memory works by looking at the phystop variable ($42E) with SID if you have the developer stuff. It should read $100000 (1M hex). Also note that memcntlr ($424) now holds 5 instead of 4, and that v_bas_ad ($44E) now holds $F80000 (screen bitmap origin). If you don't have the developer stuff, try a single drive copy and check that you get the hole disk in one buffer instead of two if the new memory does not seem to exist, use sid to deposit and retrieve words on locations $80000 and up (1/2 Meg hex). If bit errors occur, the ST bootROM did not detect the extension (it checks all bits of 512 locations by testing a psedo random sequence, before accepting a memory bank). Try to pin point the faulty chip(s) and removg the error. If it doesn't boot you`re in trouble. I`m sorry. It is difficult to give hints on what to do here. So many possibilities. Desoldering the new chips probably won't work (if the old ones were functional, the ST would still boot). Check for hidden short:circuit on the RAM pins. May also be that you have a flaky new pin connection. That's all there is... PLEASE REMEMBER THAT I HAVE NOT TRIED THIS AND I AM SIMPLY PASSING THIS ALONG FOR THOSE WHO WOULD LIKE TO TRY DOING THIS. BUT I HAVE HERD THE A PERSON IN THE UK HAS DONE THIS MOD AND IT SEAMS TO WORK OK. ****************************************************************************** A circuit modification to the intelligent keyboard power supply that allows the time of day clock to have uninterrupted power. *********************************************************************** ************* WARNING THIS CIRCUIT MAY VOID YOUR WARRANTY ************* ************* AND I MAKE NO CLAIMS AS TO ITS RELIABILITY ************* *********************************************************************** Current operating system 7/85 has bug that loads a predetermined time and date into the clock at power on and reset. ( I have been told that this will be corrected in a later version. ) power input choke ( Located at power input plug ) | | | | gnd -12 +12 +5 + Power at these | \points on all L___I---I time. I 5 I ( Limits current to max of 75ma. ) ______I v I Cost aprox $1.50 | IregI 75ohm r __I---I r | | | # r 2.2ohm gnd r -->>>---+battery ( 4 AA Ni-Cad in series - to ground) diode ( Charge current 50ma. ) The keyboard draws 20ma batterys provide 500mah ------------------- I Intelligent I I Keyboard I I Clock I I time day date yrI I I | ( continued wire from keyboard ) | | diode +---<<<-+--to on led (cut + wire of led. run this wire | | to the led and connect ) diode | | ---->>>---+ | From From pin 13 plug battery from mother board +5v to key board. 5v supply to keyboard cut wire and add diode in series with wire as shown above. The above circuit has been in my ST for the last 4 weeks with no problems. The ST may be turned off for an unlimited time and the clock will still be powered but you only have 24 hours if ST unplugged from wall ( ac supply ). Total cost of materials $12.50