Slow progress due parts and covid shipping delays... got myself two boards in the mean time so have now access to some parts. This project is now driving few other projects and got out of proportions
> Still waiting for more LA probes to be able to handle 64+ channels and do address/data decoding
> Got inverse assembler software for TLA714 and started building adapter it requires to run TMS203
> Got addons for my hot air station to heat only IC pins, not etire chips to avoid heat damage. Gives more confidence with touching these oldies - so far successfully
> As expected RAMDAC is just a stupid chip, with it removed good board chimes as normal. Chip from bad board produces image in the working one
> I am about to do same trick to SCSI controller
Next is to get TMS205 working and decode what the board is doing. With CPU, buffers and RAM + VRAM replaced not much options I see but still curious to see if it fails at RAM test as part of rom boot or elswhere. Provided it fails with RAM this would mean indeed Sonora doing mem mgmt. is bad.