Re: Star Wars Repair Story (long)

>I figured out one of the Mathbox ROMS was bad (#113), by comparing them to
>the images on tant.com. I got the correct image and programmed a
>battery-backed
>8kx8 SRAM with the data. Then I rigged a temporary board which mapped the
>bottom 4 bits of the first 1K of memory into the socket on the main board
>and voila
>- It's all better now!

(!) Wow. Now *that's* a fix. :-)

>Now I simply need a more permanent solution, as they don't make those
>signetics PROMS anymore. Maybe this is a common need?

I like your EPROM board idea from a "hacker" perspective, but the 82S137's
are readily available from JDR Microdevices and Jameco Electronics still
for about $2 each. Until those supplies dry up, I think a daughtercard
with an EPROM will probably be more expensive than just replacing the PROMs
for now.

(Frank does bring up a good point though-- there are lots of (big) EPROMS
out now that match or exceed most of the old bipolar PROM speed
characteristics for just a few dollars. They'll probably get to be more
important later on when the PROMs start to fail and replacements are not
available.)

-Clay

Clayton N. Cowgill Engineering Manager
_______________________________________________________________________
/\ Diamond Multimedia Systems, Inc. clay@supra.com
\/ Communications Division http://www.supra.com/
Received on Sun Jun 22 12:40:45 1997