exxos's Atari, Amiga & retro forum

Atari Mega ST1 (SMD Version) upgrade to 4MB with Chips 1MBx4 ...

Remove the old Chips with Hotair and remove the 8x 1MBx4 Chips from a PS/2 FPM 4MB or 8MB Simm. Solder the new Chips on the Board and connect all unsued A9 Pins together and connect these over a 33 Ohm resistor to Pin64 of the MMU, thats all.

:bravo: :goodpost:

This is similar to a 4 mb upgrade on a C103414-11 STFM board. This board has 4x 4 bit 256 kb dram’s in SOIC package (SMD) and one empty bank. All resistors are connected on this board. The one I have, has an IMP chipset so it will not support 2,5 mb of memory.

All of the 4 ram chips need to be removed and 8x 1 mb dram’s In SOIC package need to be soldered on. Connect up address line A9 (pin 5 on the dram’s) and connect it to pin 64 of the MMU (SMD soldered to the board) with a 33 ohm resistor. That’s all to it.