I exchanged some email with Hans Oranje about this and concluded that it wasn't a job that I wanted to do myself. However, in order to not waste Hans' time in the future, I decided to post a summary here so that people might find the information when searching this forum. There are two steps required to upgrade an FS-A1WX (with the default 64kB) to 512kB:
The first step is to replace the memory chips on the board with 4 x 414256 chips. I found a vendor online who appears to have these for $11, and I'm sure there are more out there.
414256 256K x 4 DYNAMIC RAM- 60 Nanoseconds SPEED-20 PIN DIP PACKAGE
http://www.electronicplus.com/content/ProductPage.asp?maincat=c&subcat=cme
The chips are soldered to the motherboard, and will need to be de-soldered very carefully from the board, after which the new ones need to be soldered in. This is a rather delicate operation, and one that I don't think I'll be doing myself.
The second step is to tell the motherboard that there is now 512kB onboard. The following is a quote from Hans:
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On the PCB are printspots like an A and B near the Toshiba enginechip. The meaning of the printspots is to configure the internal mapper in the enginechip.
A B
0 0 64 kb
1 0 128 kb
0 1 256 kb
1 1 512 kb
When A and B are connected to +5 Volt the memory mapper is configurated for 512 kb of RAM. Of course you must also change the memory from 2 x 41464 into 4 x 414256 memory chips.
The printspots A and B are not hard to find because they are near the engine
and look like wired bridges between the minus and A and B.
==========================================================================
I hope this helps.
Posted: July 31 2003, 04:01 
