14.1.2 520STFM Ram

Memoryexpansion 520 STFM

From: dbolt@my-ste.demon.co.uk (David Bolt)

I hope that's a answer and a correct specification for Atari 520STFM memory

If it's the FM, and you have a memory expansion board fitted, you'll be able to use the SIMMs easily. If not, you're going to have quite some fun. I remember doing this to my first FM 10 years ago. I ended you soldering in 16 '41256' chips and the bypass capacitors, and 3 resistors. If your motherboard is a Revision B, the memory is under the power supply. If it isn't a Rev B, I can't give any more help.

Before I say anything else here, the following is for info only. It isn't meant to be step-by-step instructions. It's meant to show just what would be needed to do the work. If you actually use the following info and it works, all well and good. If it doesn't, don't blame me for it. It's your responsibility. It worked for me but it might not work for you.

If it is a rev B. you'll want 16 41256 chips (120ns or better) and 1nF caps, and 3x 330R resistors. I also used 16 DIL sockets so I wasn't soldering onto the chips directly. I soldered the sockets into the positions marked:

U5 , U6
U12, U13
U20, U21
U24, U25
U29, U30
U36, U37
U41, U42
U46, U47(!nl)

with pin 1 to the top right (facing front to back, component side up). The capacitors were soldered into the holes to the right of each socket. I can't tell you all the numbers, as some are obscured on my motherboard. The ones that are visible are:

C18
C28
C42
C53
C60
C79
C83
C120

The last things to solder are the 3 resistors in R71, R72 and R73. After they're in, check for solder bridges and then insert the chips. Check everything again, especially that the chips are in the sockets correctly (three guesses why?) and re-assemble.

If everything went well, you should now have a 1Mb FM.