Recent content by stepleton

I'm not sure the caveat is so important: do we really need to "fully test the chip"? If we're trying to troubleshoot a fault in-circuit, then we don't care about parts of the truth table that the circuit never uses. It is probably enough most of the time to discover a fault in a chip's ability...

@ibm5100 If it's making it through all of the power-up tests, then it's reading the ROS OK and validating its checksums/CRCs. Are you certain that this isn't a display problem with the bottom of the screen? What happens if you boot into APL and then press the EXECUTE key a bunch (to scroll the...

Apologies if this has been pointed out before, but Tektronix liked to use those miserable TI "side-wiper" IC sockets which many people find unreliable, and I can see some empty ones on your circuit board. You might want to include the possibility of a faulty socket in your troubleshooting.

This description matches my understanding based on the Lisa Hardware Manual. There are different versions of this document, but I think the MMU details are pretty much the same: https://bitsavers.org/pdf/apple/lisa/hardware/Lisa_Hardware_Manual_Sep82.pdf (PDF pages 27-39, 117-124)...

I put this forward in the hopes of learning from being corrected, but can't you map segments in multiple hardware contexts to the same physical memory segment? The Lisa OS does have shared libraries or "intrinsic libraries" as they call them, but I don't know how they work. I think I assumed...

5100 BASIC does not have PEEK and POKE unfortunately, but you can break into the built-in Diagnostic Control Program (DCP) and manipulate memory directly. This includes keying in programs in PALM machine code and executing them. Writing PALM programs like the one you describe should not be too...

I don't know from looking at compiled code, but the Lisa has a homemade MMU in discrete logic that can do address translation, so I'd guess relocatable code is not a priority and may indeed not be an approach that Lisa binaries take. (Yes, an MMU with a 68000; if software did any kind of memory...

Per the video, well enough to get them to run and survive eight hours of the built-in "monkey" testing (think fuzz testing). The biggest difference has been that the spellchecker for LisaWrite is not available: we never got the source code or data files for that as it presumably still belongs to...

Quite possibly! In the presentation, Alex mentions working on a fix to the infamous Lisa Y1.995k bug.

William Tooker and Alex Anderson-McLeod (aka @warmech and alexthecat123) have successfully recompiled the Apple Lisa operating system and the Office System desktop manager (think Finder) and tools (think applications) from the source code released a few years ago (thanks @Al Kossow ). Recording...

I use it (or derivatives of it) because it's a convenient OS to use for the RC2014 Z80-based kit computer. There are more modern elaborations of CP/M that some people in this community use; they're not strictly for the RC2014 only, that's just where I know them from. I don't really use them all...

I did. It took about a month to work up the courage. The machine still worked. This is the same computer that I was asking about in the tin whiskers thread: it seems to have weird problems now and then. The disk was playing up a few days ago, but that was probably due to the hot weather. When...

I'm glad if my approach has some useful elements! I am not 100% certain of how to use the sockets you've described --- is there a way you could show what you have in mind via a drawing? Currently, when viewed from the side of the PCB with the connector facing down, my current connector uses...

Would it be worth reconsidering then some elements of my approach? Integration with a PCB at a right angle is intrinsic to my design; you get it "for free". Mechanical and electrical connections are accomplished with solder. With 24 individual solder joints, it's a pretty sturdy assembly. I...

An incredible development! I am impressed by how few ICs there are. Best of luck ironing out the last few bugs, and I'm hopeful I'll be able to upgrade my 5100 (with its different logic) from 32k to 64k at some point.