Recent content by dougg3

Yeah, if the ROM is accessed after OF is up, it would be tricky to add a switch because it's game over after the switch is flipped to the second ROM. If you can prove the ROM is not accessed, or guarantee to not access the ROM after a certain point and give the user a chance to flip the switch...

The quickest path I see to testing something in an ANS is to whip up a ROM DIMM board with eight PLCC sockets. You could use something like SST39SF040 chips programmed in an external flash programmer. That should cover the full 64-bit data bus and give you 4 total megabytes of ROM space to work...

Something that was pointed out to me a while ago: this PCI Power Macintosh DDK disk has a TNT version of Apple's Flasher app on it. Probably mainly useful for reflashing a flash ROM DIMM that you're already booted from, but on the off chance that it gives you any extra context I thought I'd...

Interesting! It appears that the DCB structure also allows just setting it to an arbitrary number, according to Microsoft's docs. For example the CBR_115200 constant is simply defined as 115200. It might be worth trying to patch the code to see if assigning 230400 "just works" for you. It does...

Happy to help, it's a fun little puzzle. Here's a little mini deep dive further into it. I thought about it some more, and I think I have a reasonable guess about why they got rid of it on the 520/550 board. Looking at the CC schematic, populating only R75 would keep VPP at 12V at all times...

My assessment is that R80 only matters if you are using a ROM SIMM. It shouldn't matter for any kind of overclocking or conversion from 520 to 550. Its sole purpose is to put +5V onto the VPP pin of the flash chips used in ROM SIMMs of the era. Usually the flash chips like to see something like...

Yep, this is definitely the same circuit as the CC. I just beeped it out as best as I could on my 820-0368-A board from a caddy-loading Performa 550 (3.6V battery, R80 not populated, for the record). J12 is equivalent to CC's J12 Q1 is equivalent to CC's Q3 Q6 is equivalent to CC's Q2 R9 is...

That pin (pin 2) on the ROM SIMM socket is VPP, which is 12V power for allowing EEPROM chips of the era to be reprogrammed in-system. Pin 2 was also the A0 address line on older Macs, but Apple began using it for VPP in the Quadra era, presumably after realizing that A0 and A1 didn't need to be...

I'm glad you got something working, @JDW! I know I said I wouldn't derail the thread, but just wanted to add one more thing after your latest discoveries: to be clear, I don't think this is a USB problem at all. The fact that you are seeing good communication with the programmer software means...

Uh oh! Unfortunately I don't have an actual machine running High Sierra to test against, but I can confirm that in my High Sierra VM it also isn't detected properly. It works correctly on my Mojave VM, as well as my M2 Mac mini running Sequoia. I just flashed and verified a programmable CayMac...

It's for a ROM SIMM that could override the soldered-on ROM chips. Most 475 boards I've seen don't have that socket populated; you might have an early board.

For what it's worth, on the ADB side, bbraun discovered back in the day that the TechStep sends a special ADB command on machines with an Egret/Cuda to enter the test manager, which can't be sent with a normal keyboard...

I'm going to go out on a limb and guess that you are using a custom ROM SIMM in your SE/30. With a custom IIsi- or IIfx-based ROM in an SE/30, System 7.5 and up will hang at Welcome to Macintosh until you patch a couple of system files with ResEdit. bigmessowires saved a copy of Gamba's page...

For what it's worth, I recapped my Macintosh TV's analog board (also "630-0355-") back in 2013 and CP14's orientation matched your picture. I put it back in the same way as the original and it worked fine. There was no revision sticker at all on the board. Here's a picture of how it looked...

I don't, but it sounds like you've got your bases covered!