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Re: Laser 2001 & Salora Manager - official thread

Posted: Fri Jun 11, 2021 2:47 pm
by Gabriele72
ROM3 replaced by my custom ROM, at times succeeds in programming the VDP but locks when accessing RAM.
Maybe something messes with the bus, or some bad solder... an almost impossible problem to track down :|

Re: Laser 2001 & Salora Manager - official thread

Posted: Sat Jun 12, 2021 5:55 am
by Scouter3d
Hi Gabriele72,

gratulations! Wow! a RAMtest BIOS!

Maybe it is a busbuffer/driver 74LS244 or 74LS245 (i have seen a lot of faulty 245s) or a RAM chip?

You can try piggybacking a stack of 2 known good RAMs over the onboard RAMs (one at a time) and test if your RAMtest behaves differently (this trick sometimes works to locate a bad (unstable) ram...)

Sometimes this also works with logic-ICs so you could try stacking the 244s and 245...

Ciao, TOM:0)