🚀 go-pugleaf

Stephen Matson asked about expanding the memory in a 520STFM..
 
The first step is to unsolder all 320 holes that Atari conveniently
soldered shut for you..
 
Then, for safety's sake, install sockets in all RAM locations.

The bypass capacitors aren't particularly critical.. use small
form factor .01 mfd units to make them fit..

The RAM chips are 256K x 1, 150 ns units.  You can install faster chips
if can get them cheaper..
 
The last step is to install three resistors in the RAS and CAS lines
from the MMU chip to the new RAM bank.  I forget the exact values of
these resistors (don't have a 520STFM myself), but they're in the range
of 150 ohms.  There should already be three resistors going to the
existing bank of RAM.. check to see what these resistors are, and
emulate them in the new installation.
 
That should be it.. the operating system will recognize the new RAM
automatically.. you don't have to do anything special to get it to
see the full 1 Meg of memory..
 
Lastly.. enjoy..!   (You'll love the new freedom of all that memory..!)

BobR