I think it is a fix for IORQGE - as that signal wasn't good from the ULA for some batches - but it's been some time since I've looked at the old boards

I don't get the impression he was ever aiming to make a QL - just a minimal chip count 68K based computer - so goal achieved.

Testing the RAM chips is a good idea, but only tells you the RAM chips are working - if the issue lies on the board itself, then you won't see the fault with the RAM chip out of the spectrum.

Power supplies, glue logic, even just something stuck on the PCB could cause the issue.

If it's processing through the ROM then yes. What you really want is a plug in cartridge or similar that has it's own ROM in it - see if that gives a legible display. There is a good diagnostic ROM for the spectrum (well actually several), that will attempt to test cpu, memory, screen etc. This will...

I wonder why they went for a 68008 instead of a 68000 ? It was a screwup and mismanagement. Clive thought he could do QL with 64K RAM as a fot in the door and with substantially cheaper 68008. But when it came out, 68008 was _more_expensive than 68000. Also, 128K in QL used 16 DRAM chips. And as it...

That's very similar to the 'blackout screen' you get just before the prompt comes up. Suggests that it's having an issue somewhere, as you are not seeing a fully black screen.

Probably the ease of connecting an 8 bit bus rather than a 16bit one, and also the pic is emulating the boot rom forthe 68K part

I was looking at the Minipro - there is a Linux version of programming tool on GitHub - I think they may use a different method to define what chips it can program, as the Windows executable uses just a single DLL file with all that info in it. Still trying to get my head around what is actually in ...

I think you can program those EPROMS, but you won't be able to erase them as they are probably the OTP type - if there is no Window on the package, then these are one time only programmable - so no erase - just program then verify. You may also have to turn off ID notification checkbox on the TL866 ...

The display pattern suggests the ULA is working well enough to provide video signals with correct sync, and the coloured squares show the attributes memory has some random data in it. Since this is the 48K model - the video is coming out of the lower 16K contended RAM. Are any of the major chips soc...