That’s really useful, thanks
We’d certainly tried the minimum config setup earlier in the debug process when we were swapping chips between broken and working machine but yes it makes sense to go back and try that again. Good reminder![👍]()
next chance to spend serious time on the machine is this weekend so hope I can feedback in a few days - thanks again
We’d certainly tried the minimum config setup earlier in the debug process when we were swapping chips between broken and working machine but yes it makes sense to go back and try that again. Good reminder
we thought the lower 16k looked ok so we were surprised that none of the s25 jumper options (or using an inverter, or piggy-backing DRAM) would make the machine boot with the OS ROM. Thats what started us further down the path of address line logic / checks as clearly one or both of these are falseIf the DRAM at 0x0000 to 0x3FFF is working and there are no problems with the multiplexed DRAM address lines to the DRAM, the machine should be able to start up if configured for only 16K of DRAM.
We’ve definitely checked there are signals on the address lines but I don’t think we’ve compared them to anything else yet to see what’s ‘good’ or ‘expected’. Is there any reference in any of the fault finding guides we may have missed ?However, due to the multiplexing (which is complex in a Beeb), one or more of the address lines to the DRAM chips may be getting mangled. Have you checked these with a ‘scope?
next chance to spend serious time on the machine is this weekend so hope I can feedback in a few days - thanks again
Statistics: Posted by eddawes — Wed Apr 02, 2025 10:07 pm