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(deleted) -- had a note here that the patch might not work because I missed a register restore but realized I was looking at the wrong section so ignore this post. Hope that patch results in a proper boot. Let me know.

Yeah, I opted to leave the checksum as I was told certain things attempt to look at the checksum to make decisions (machine identification). Computing the checksum is straightforward so could definitely skip the checksum check and just overwrite the correct new checksum.

@ViperLord try one more thing. I'm not 100% positive I got these offsets right... but try patching these two locations instead (ie. only do the checksum disabling patch and the following two below) Offset 0x44714 ... change 2448 to 4ed6 Offset 0x44822 ... change 2449 to 4ed6 These two patches...

I think you're right. Without writing to all the memory locations once, the parity bits would be wrong. The parity bit is read/written by hardware. The two memory tests are oblivious to the parity bits if memory serves me correct. They just repeatedly write a pattern to all of the memory and...

The two patched routines just perform a memory check (one in ascending direction and one in descending direction). The patch just returns from them immediately without running the test. If any errors are encountered, one of the registers holds this state. I'm not sure why skipping it would cause...

@frontein1 is probably right. I've confirmed the patches are working fine on my IIci but I also do not have a parity model. Skipping the memory test procedures must be skipping some step required by the parity check later.

The above change I had done skips the routine. Or did you still want to run the routine but return a pass?

Yeah, haven't repro'd on floppy but I have not tried it enough. I need to.

I have to admit I have been eyeballing the Portable... the only thing that holds me back is tunnel vision. My 8500 was very brittle, just like the 800/840AV. The design is very similar. That said, my 8500 is holding up after some epoxy, etc. Having used it to work on the 8 * 24 GC patch...

That’s weird. I have a flashed ROM working fine in my IIci. I will reconfirm with my ROM and make sure I didn’t make a typo but if the stock instructions at those offsets match, I doubt it’s a typo. Can’t look til tomorrow but will check.

Starting a work thread for debugging multiple issues with my Quadra 950. State Upon Receipt I picked this unit up online and it came in a non-working state. The power supply was dead (various issues on both the primary and secondary sides). ATX Power Supply Put together an ATX conversion of...

No. This is only to resolve the artifacts during drags that impact the 8 * 24 GC with Drag Manager.

Created a system extension that resolves screen artifact issues when using Apple's 8 * 24 GC video card with drag and drop on System 7.1 or System 7.5+. Issue was described in this thread: https://68kmla.org/bb/threads/patch-8-24-gc-control-panel-for-compatibility-with-drag-drop.46344/ Will...

Got it working. It's now a system extension of its own. It does not replace the normal drag and drop extension. Both must exist. I have tested it on System 7.1 on a IIfx running the 8 * 24 GC (rev 2). I also tested it on System 7.6.1 and it works there too -- obviously for System 7.6.1, the...

Well duh... there's a better way. I'm going to create a new system extension which wraps the DragDispatch trap to add the enabling/disabling of the acceleration. That should be cleaner as it avoids patching the stock system extension, and hopefully work on System 7.5+ as well.

Wow, been a year.. but finally found some time to disassemble the Macintosh Drag and Drop system extension as well as the 8 * 24 GC control panel. I was able to reproduce the following two artifacts when running the 8 * 24 GC with acceleration enabled while at the same time having the Macintosh...

Spot welding batteries is easy and the welders are fairly cheap on Amazon. The EMM board is finicky tho and prone to failure. The memory chip is replaceable but not the EMM custom chip.

Well, I guess I can get down to 9 if I can fix the 950. Speaking of which, borrowed a stock 950 power supply from @techstep and immediately reproduced the issue so that rules out the power supply. Which means something is wrong on the logic board since the memory, drive, power supply, ROM, have...

This is very close to where I have been landing.. SE/30 IIfx Quadra 700 PowerBook 540c Power Macintosh 8500 and then as I sit there staring at the machines to drop and then the emotional aspect like what @akator70 plus some subtle things start kicking in... and I add back in: SE - the...

Interesting reading all of your thoughts. Lots to chew on.