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A logic analyser is a very useful thing to have indeed! I don't think that what you have here tells us much more than we already know, though. All of these signals look correct to me. We will have to check something else. ----- Meanwhile, your 'scope screenshot shows us what we expected to...

I couldn't resist studying the code just a bit more. TSTLOOP and MMUERR are dead-end routines. If the CPU winds up executing that code, there's actually no more testing being done: it's already decided that the MMU is in bad shape. What it's doing is bouncing on \RESET so that you (the...

Thanks for making all of these measurements! I think we may have made an important discovery. From the looks of things, something seems to me to be reading the ROM. That's great news, but: the \RESET pulses seem odd! But there's a chance that they could have a valuable explanation... keep...

I hope it's not unkind to ask: have there been any developments in understanding 6100 incompatibility? Did it turn out that the 7100 and 8100 have similar problems, or are they immune?

Your video board appears to me to be in great shape: it's drawing a nice, crisp display for you. It's just that the video data that it's getting from the CPU board is nonsense. The nature of the nonsense (and the reason it's different all the time) is because it all depends on whatever...

Looking further ahead, here is a kind of plan we might undertake. There may be simpler ideas, of course! I suspect that the problem we're dealing with is in the Lisa's MMU, which as Larry Pina notes is what uses the static RAM that we've been worried about. If we find that the Lisa is executing...

Ah, well that's great news. It sounds like the probing plan is back on track! Also for @BEU : An update to probing the ROMs. In the Lisa, a look at the schematics (PDF page 3 of http://www.bitsavers.org/pdf/apple/lisa/hardware/050-4009-F_CPU.pdf) shows that the ROM chips not only have a \CE...

Not a bad idea. If you know someone with a Lisa of any kind, the CPU and memory boards should basically be interchangeable. It's only the motherboard and I/O board that are substantially different, and where you will need to find someone with another 2/10. I think though that the problem is...

No worries. I am glad that you are up for this challenge! As for your documentation finding, that's very interesting --- and I stand corrected about not having any written low-level diagnostic material! I think this MMU register issue sounds like a very plausible theory to me. I expect that...

I am not writing all of this stuff because I love to type! I'm writing it for you. If we are going to solve this problem together, then I think you'll need to play an active role as part of our troubleshooting team. It's not going to work if I'm just giving you instructions from far away ---...

There's no harm in testing continuity anywhere on the board, but the suggestion to check around the CPU and the static RAM was basically @mactjaap 's little joke. What @mactjaap did was put your initial post into an AI chatbot, which generated a fairly generic answer that wasn't really based on...

:rolleyes:

Hmm. It does seem like a logic problem. The Lisa has many more ICs besides the 68000 and the static RAM. If you think of it as a numbers game alone, changes are that the problem is with a different chip! So you've got a classic troubleshooting problem on your hands. The usual thing to do is to...

I have a competitor device in a Portable, called the "VideoMacPac". @apm cloned it several years ago. It definitely initialised the CPLD in the way @SuperSVGA describes: you need the control panel to download a binary blob into the device. This card looks very similar, although there's a chance...

This is ridiculous! IBM's repair manuals at least extended the basic courtesy of giving you instructions for how to save your co-worker's life: "Continue without interruption until victim is breathing without help or is certainly dead." --- not a phrase you expect to find in documentation...

Yes, that's my Lisa 0. It's really just cobbled together; I don't have schematics for it. Here's a clearer photo that lets you see the resistor values better: https://photos.app.goo.gl/vDfeNUc8rLhM5PMA9 Get a pinout of the Lisa PSU connector and go to town! (Check on Bitsavers or...

Thanks for this introduction! How are network numbers chosen, and how does a computer joining an existing AppleTalk network learn what the network number is?

The only way to access a disk with a Houdini II card is through BIOS calls. If your OS doesn't use the PC BIOS to talk to the disk (and Linux doesn't), then you can't really run the OS. But if you must have a Unix-like experience, some very old versions of Minix can be configured to access the...

Here's a less risky approach to consider: 1. Take a look at the servo board schematic; maybe find a friend who likes looking at schematics if this is new for you 2. Identify the signal line that carries the coarse servo positioning information from the arm to the servo board 3. Practice using...

I suspect NeoWidEx will not tell us very much at this stage --- the servo is probably not reporting that it's in good health, which means that the controller won't be ready to talk to the Lisa or to NeoWidEx. But it might be worth a try. Here is the haystack where we will need to look for our...