After the last discussion about T600 I made a few different variations
on model 600 ram, from an all-through-hole version to a micro mini
version where all the actual logic and ram chips fit entirely within the
footprint of the bus connector, and a version that bridges both
motherboard connectors and provides all 192K from a single part.
I'm still waiting for a few parts I forgot to order to test the tiny
version and the through-hole version, but I was able to build and test
the dual-bank version and it seems to be working.
I don't have a proper memory test program so all I'm doing is copying
large random files from a pc to ram on the 600 by xmodem to fill up the
200k, and back to the pc and comparing against the originals. So far so
good.
I haven't verified the electrical behavior with a meter or scope yet
either. Like, are the chip-selects working as expected to disable the
chip during main power off, do the waveforms look good, decoupling ok
etc. But outwardly at least it's functioning as expected.
https://github.com/bkw777/TANDY_600_RAM/blob/main/README.md#dual-version
https://photos.app.goo.gl/Lm2r2ftutK75Xy9K8 (latest pics at bottom)
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bkw
