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Very interesting. Any chance you could take a photo?

On other forums @techknight has said: "What I need you to do now, is check the voltage at the Hybrid, on the pin literally behind the NMI button. it goes into that Op Amp sitting below. It should hover around 2.2 to 2.5VDC. if it falls to 0, or latches at 5V, the system will NOT stay on. If...

Yes. I believe there is an analog voltage provided to the PMGR that represents some fraction of the battery voltage. This allows the PMGR to know when the Portable is plugged into an outlet and to be able to measure battery discharge levels. I believe this also allows the PMGR to soft shutdown...

Last night I went through the Macintosh ROM source code to see if there were bug fixes related to this. While there are plenty of fixes related to inverted text, I didn't find an exact match. In any case, the patches were applied before System 6.0.8. What I did discover was that Apple routinely...

Have you tried running MacTest Pro? It has tests for the video card as well as the computer itself. I usually click the Deselect All button followed by checking the video card, logic board, and ram tests.

This is crazy. Same computer, disk, memory size, video card, slot D, monitor adapter, and monitor. Different results The only known difference is in your parameter RAM. You have a couple of bits set in byte 11 and somehow you've got 32-bit memory set on a 32-bit dirty computer. I assume...

Attached is a disk image I used on a Macintosh IIx with the same ROM and the same Apple Display Card 8*24 (with the same card ROM as you have pictured in your first set of pictures). I do not get any garbled text.

This is unlikely to be useful information to anyone. However, in the event someone is trying to get around an incompatibility with the Apple 8*24 GC graphics card, this may provide clues. Running System 7.1 on a Macintosh IIci, with 32-bit addressing, correctly named 8*24 GC control panel...

Awesome!

@campbellashe Do you have a M5126 backlit Portable? I think you'll want to add a 7MB jumper option, as that model has an address conflict that prevents 1 MB + 8 MB.

That's what we suspected. So, if you average the clocks (2 + 6 / 2 = 4) over the entire memory range, you end up with the 50% slowdown (4 instead of 2).

Incredible work! No init needed. The 5120 Portable has a one wait state. You must be driving your 8 MB at zero wait state. That's why it is even better than the 1 MB card.

According to Apple's technical note: "Unlike the original Macintosh Portable which required one wait state, the backlit Macintosh Portable requires zero wait states when its processor is accessing memory locations in the expansion RAM." "It is possible to expand RAM up to 8 MB, however the...

Let me try to summarize your findings: 1. The slowdown occurs even on a non-backlit Portable. (Previously, I thought this was a backlit problem.) 2. Speeds are: A. 100% with no memory card (1 MB onboard) B. 85% with +4MB memory card C. 51% with +8MB memory card D. 22% with +8MB memory card...

@SuperSVGA is the expert on this. He stated "Any access at all is sufficient, such as a simple tst.w $FC0200 instruction or running DM FC0200 from the debugger." Can you try using Macsbug and testing the DM FC0200 instruction to see if that speeds up your card? - David

I just checked it out. Perfect.

Cool. Glad you found the issue.

Interestingly, for the broken images, they display the text of the link. Whereas the working images display the image.

Really cool! Aside: Doesn't quite work in the Firefox browser.

It works!!! 1 MB onboard + 3MB on the full Apple RAM board. Here is one side of the RAM board with 628128BLFP (to be clear 628128BLFP as opposed to the original 658128ALFP) chips added. Eight chips added to each side for a total of 16 chips. It increased the memory on the board from 1 MB to 3...