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One suggestion I have for troubleshooting is to start out by flashing a stock Q650 ROM to the programmable SIMM just to rule out any hardware issues and prove that the SIMM and socket are both working fine. I'm guessing you won't run into any problems with it, but it might be a quick way to rule...

Thank you! And I forgot to mention here, if anyone else has a Performa 550 (or even potentially a 57x model) I'm still very curious if we can find out if there's a special lost version of Apple Backup that created it, or if it also has the recovery partition.

I found some time to write up everything and also shared as close to a factory-fresh drive image that I could create, so anyone else can download and play with this functionality in MAME. The recovery partition even works on the IIci and the Classic II, verified on hardware...

Some earlier models had the socket populated even though there were also onboard ROMs. My guess is they were trying to future-proof just in case there was a nasty ROM bug, and they stopped populating it after they were confident the ROM was good. Just a guess though. Apple designed it so that...

The search is over, and this elusive recovery partition has been found! A kind person on Reddit let me borrow the hard drive from a Performa 550. The Conner drive did not want to cooperate, but I opened it up and figured out how to unstick the head and dumped it. More details, and of course...

I second that -- if any of the boards are a lost cause, please save any of the custom chips you can. I'm sure they would be useful for somebody. I accidentally fried the flash /WE pin on my LC 475's MEMCjr (343S0164-a) chip by putting 12V on it (oops).

For sure. It's an interesting question to ask. For example, did the Performa 560 come with it? What about the Performa 57x series? I wonder if the issue they ran into with that second technote made them decide against continuing on with this concept. Either way, I find it very interesting. If...

Hi there, I wanted to alert everyone about an unpreserved piece of Mac history that Pierre Dandumont first told me about. The gist of it is that according to Apple, the Performa 550 had a hidden recovery partition that it would boot from if the main system folder was screwed up. This hidden...

Nice! Just to clarify, it's not my PCB design, but I can confirm it works :) Also, for anyone who might be shopping around for connectors, I originally bought some DA-15 connectors that didn't fit properly. The ones I linked above have a 10.3 mm backset spacing and are correct for this PCB. In...

Here's what Apple said the pinout of the cable was supposed to be. The only difference compared to the pinout linked in the OP is the grounds are handled a bit differently. Not sure if that would explain the passthrough issues, but thought I'd mention it. I don't have an original cable to...

For what it's worth, earlier this year I found this shared project at OSH Park by Zuofu and made a few. It works great with my Centris 610 with a Houdini I card. I'm pretty sure the Houdini II pinout is identical -- after all, the project on OSH Park says it's for the 6100. Here are the parts I...

Hi, I'm the author of the SIMM Programmer software (@JDW pointed me to this thread). As an alternative approach to Kay's excellent suggestion above, you can also accomplish this by clicking the "Flash individual chips..." button in the main window. This takes you to a new screen where you can...

Amazingly enough, I actually asked for help with this same question on reddit many moons ago: The helpful information that I received was that the star logo on the top is Hosiden. One person suggested the HSJ0914-01-040 might be the part number, but it doesn't look like a perfect physical...

Interesting, I hadn’t noticed that the stock VRAM was different between the two. You’re right, the CCII has 256 KB and the 550 has 512 KB. They’re listed as the same service part (661-1830) in Apple’s service source stuff, as well as this module identification guide...

The Color Classic II and LC/Performa 550 all used the same logic board and ROM. I'm pretty sure that's exactly the kit you're looking for.