4MB RAM upgrade for C103414-001 Rev 1.1 (520/1040 STFM)

[jwd]

A good video upgrading exactly this type of memory chips



I have it bookmarked as I'll be doing this on mine at some point, i got the chips from a 4mb falcon memory board as the chips were marked the same as in my ST.

You really need a diag cart and see what the output is via serial probably one or more chips not right.

[MaximilianM]

ah thx nice video, and yeah i conntacted my local dealer, maybe he has a diagnostic card... without its pain in the ass...

[MaximilianM]

Quick update: got the Atari Bombs Away diagnostic cartridge and tried it. Instead of the expected diagnostic menu, I get a different error pattern on screen — static vertical color bars, not the usual half-black/half-noise I had before. Reset button does nothing while the cartridge is plugged in (works fine again once I pull it).

Does anyone know which RAM bank or which specific RAM IC is tied to the video/screen memory on the 1040 STFM? Trying to narrow down which chip to focus on. Thanks!

[DoG]

Connect with another computer via null-modem-cable to get output from diagnostic cartridge. RS232-USB to PC for example also work with a terminal program.9600 baud,8N1 (8 data bits, No parity, 1 stop bit). No flow control

https://www.atari-wiki.com/index.php?ti ... dge_basics

(Then the basic: clean port and cartridge with isopropanol, set 'bombs away' to (mega) ST 4.4)

[MaximilianM]

thx! it works, an endless error message...

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[DoG]

Looks like bit 7 is wrong. Written a 1 and read as a 0. Since you have nothing on screen it's bank 0. So chip U4, DQ4 (pin 25).

But I don't have schematics for that board so check with a multimeter that it's actually bit 7 on bank 0 that is U4 before you desolder it.