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Ah, thanks for the heads up. Guess I’ll just have to log on daily :)

Oh that’s true! It’s been so long since I’ve looked into this, I’d forgotten that we still haven’t tested the 1024 refresh mod for RAM ICs which require it! You’re referring to the aux board? If so, I can try to get one made up and tie it into my prototype board. For some reason, I haven’t...

Looking forward to building one of these up, installing it, tossing my defective prototype in a box, finally buttoning up my Mac, and having some workbench space back :) Great work, Builder68!!

YES!!!!! I’m so glad you were able to get the full 4MB working! Thanks for humoring me by testing with the Mac Plus style refresh since we spent so much time trying to figure that out. I’m also glad you were able to simplify by using the system’s stock refresh. I would still really appreciate...

Here is the same link on Internet Archive from before MacGUI locked down their articles to signed in users only: https://web.archive.org/web/20220711020335/https://macgui.com/news/article.php?t=470 The noncontiguous-ness isn’t a problem for 512Ke systems, but it is for non-e systems. It’s not a...

Do you have this software? Maybe this part of the circuit has something to do with the RAM disk?

I'm trying once again to understand this portion of the circuit for the MacSnap. The output of the 74LS259 controls OEb of the 74LS253. OEb of the 74LS253 being HIGH forces its output Zb LOW. Output Zb of the 74LS253 being LOW forces the 74LS139s to only provide CAS to either CAS2F&CAS3F...

I’m so glad it worked!

Where did you find the ROM-inator patch? I can only find fully patched ROMs. Is that what you meant? I wish the source code for that project was made available. In either case, for those who have a 512K/128K with greater than 512KB of RAM and want to use the ROM-inator, it should be trivial...

Looks great! Can you test out the 512 and 1024 refresh modes? I understand your particular DRAM will not make use of the 1024 refresh mode since it doesn't have the extra address pin, but I'm curious to know if it all still functions okay. I finally finished soldering up a prototype with my...

The trick would be trying to fit this routine within the same number of bytes which the ROMinator uses for its routine. Or branch to some location in ROM which has enough unused space to fit this routine, making sure to return at the end of it. Also be sure to not destroy register data if that’s...

Interesting! So it’s essentially checking for ROM mirroring at the address at which the SCSI IC would reside. Getting back ROM data indicates ROM mirroring, thus no SCSI. Getting back something other than ROM data indicates no ROM mirroring, thus SCSI is present. Very clever! I wish the creator...

Excellent! Looking forward to seeing your results. In the mean time, I’ve been slowly wiring up a soldered prototype for using two AS4C1M16F5 ICs for 4MB (disabling system 512K). I received them as well as the DIP breakout boards last week. We’re both working off very similar designs at this...

Great work laying out these PCBs! One thing I spotted is pin 1 on the aux board’s ‘253 should be connected to DMA instead of ~DMA. I think the ~DMA signal is also accidentally connected to a signal used as a pull up for a bunch of other inputs. Other than that, it looks good to me! I haven’t...

I concur! Two smaller boards would be advantageous for all the reasons you mentioned. I’m excited to see how they turn out!

Are you saying you have a Dove SCSI add on board as well as a memory expansion? If so, do you think you can fit the ROMinator on top of the SCSI add on board (if the pins align with the IC sockets) to test that?

Mine is the SUPERMAC TECHNOLOGY SCSI board, and It uses Mac Plus ROMs. I think all SCSI upgrade boards for the early Macs use Plus ROMS? Someone successfully reverse engineered the MacSnap SCSI board: https://68kmla.org/bb/index.php?threads/reverse-engineering-the-macsnap-scsi.37901/

I wish the 5380 SCSI controller had a device ID register to read to check for it. I’m not sure it can be done in the same number of bytes, but maybe there’s a register in the SCSI controller to which we could write a value and then read it back to confirm that it’s really there. Hopefully...

Do we know if the ROMinator is still supported and if the author would be willing to investigate a fix? As an aside: If a Mac 512K with greater than 512K of memory also had a SCSI upgrade board in place, would the ROMinator work with it?

Did you mention in a previous reply that you did get the ROMinator to boot with the RAM expansion but only when it was configured to only provide 512K?