Fast! CompactFlash for Macintosh PDS/NuBus

[opualuan]

This is great to see! Would you consider adapting a version for the LC III PDS? This bus is inside a lot of different systems, many without nubus. Adding ethernet on the same card would benefit the LC475 and other expansion-constrained systems immensely!

I’m also interested in Nubus for IIci to replace my complicated ATTO nubus scsi setup.

 

[zigzagjoe]

Funny story, it works directly on LC PDS with a simple passive electrical adapter and an unmodified ROM. So it's definitely possible.



It's a bit less compelling on LC475 though as the onboard SCSI is more competent at the same time as the 68030 bus is slower to access from the 040 CPU. So the current 16 bit NuCF card ends up fairly similar to the onboard SCSI. I can't recall if it turns in an advantage on small/random accesses still; the 040 CPU went a long ways towards reducing the impact SCSI manager had on throughput.

I'm planning to make a simple nubus test board for me to test 32 bit access along with some other concepts and see what avenues that opens up.

 

[opualuan]

Nice! Very interested in what you find.

 

[Pushpull76]

@zigzagjoe Hey, very interesting project! Did you ever tested it in a IIfx with a bunch of Digidesign nubus cards in it?

 

[zigzagjoe]

@zigzagjoe Hey, very interesting project! Did you ever tested it in a IIfx with a bunch of Digidesign nubus cards in it?

I haven't specifically tested on IIfx with digidesign cards, but conceptually it ought to work. Production of these are on hold due to tariffs however.

Not entirely bad timing as I seem to be running into an issue with a minority of IIfx logic boards - the afflicted systems have a glitchy /AS signal which is causing cards to not work reliably. Interestingly, putting a pull down resistor on /AS seems to help, but I haven't been able to quantify why as even putting my LA probe on the /AS signal is enough to also cause the issue to resolve.

There seems to be some precedent for this aside from IIfx generally being a finicky beast.

From MacWEEKV07N20:
"... a 33-MHz '040 card for the Mac llfx. The latter model, the TokaMac II FX 33, requires a slight alteration to the llfx motherboard...."

Also this post:

Anybody here ever run a IIfx with A Tokamac accelerator?

Many years ago I snagged a Tokamac IIfx PDS card (2004 ish). The software was vaporware for it so I contacted the original creator (Andrew W Donoho) and he sent me the correct drivers for it. He also told me the IIfx motherboards had defects from the factory with respect to bus mastering so you...

68kmla.org

The PAL in question is the one that also generates the /AS strobe for the IO bus/PDS so it's plausible there's an issue affecting both with the logic. I'd be curious if any of the SCSI Bolt (iifx PDS SCSI) card manuals exist and/or reference a similar problem.