SCSI emulator for '030 accelerated Plus?

[JC8080]

Moving this post to its own thread, I originally added it to an existing post on a related topic and probably few people will see it there.

I have a Performer clone I built that works fine in my SE, and I recently installed it in my Plus. The machine works fine booting from my BlueSCSI v1.1 without the accelerator drivers installed, when I install the drivers (I have tried GemStart 2.2 and 3.0) the machine freezes as soon as I try to do anything (copy a file, open the control panel, etc.) Based on this experience along with the info in this thread, it sounds like maybe BlueSCSI is just not compatible with an accelerated plus. Does anyone have any idea if any of the other SCSI emulator solutions will work with an accelerated Plus? Floppy Emu also does not play nice with accelerators, so at the moment I don't have a way to use this machine accelerated. Unfortunately the floppy drive in this machine does not work, it probably needs at least a cleaning, and I have not had a chance to try that yet. I suspect it would work fine booting from a floppy with the drivers, but I cannot confirm at the moment. Does anyone know if the BlueSCSI v2 has the same compatibility issues?

The Plus has the diode mod and the BlueSCSI is powered off the SCSI bus. The BlueSCSI has the correct Plus .ini file in the root folder. I am running System 6.0.8. The analog board is freshly recapped, and with the accelerator installed and BlueSCSI hooked up I am seeing 5.2v and 12.7v, so I don't think there is an issue with low power.

Any help would be much appreciated!

 

[bigmessowires]

I don't have any answers to your questions, but as you probably know the Mac Plus SCSI is weird. BlueSCSI and ZuluSCSI need a special config to support the Plus, which you're using, but it wouldn't surprise me if that special config doesn't work for an accelerated Plus. As I dimly recall, the weirdness about the Plus SCSI is that it does blind transfers with hard-coded wait times instead of checking for completion of SCSI operations. So an accelerator would certainly affect that.

Floppy Emu should work fine with accelerated Macs when the Emu is emulating a floppy drive. It will not work as an HD20 hard disk if the computer is accelerated, though.

I don't know anything about this Performer clone, but is it supposed to work in a Mac Plus? As I understand it, the accelerators need to patch some routines in ROM in order to work correctly, and the Mac Plus ROM is different from Mac SE ROM.

 

[JC8080]

The Performer clone is designed to work in a Plus, SE, or Classic. The original was reverse engineered by Bolle, here is a link to the page if you are interested. This same card works fine in my SE using the same boot disk with the same drivers, which definitely makes me think it is a SCSI incompatibility due to the SCSI weirdness you mention above. I am going to see if I can find a different driver version that may work, though I don't have high hopes.

Crutch over on TD said they have had success with multiple accelerators in their Plus using a SCSI2SD. Unfortunately the SCSI2SD is not made any more, though the ZuluSCSI is a similar product. I reached out to the creator of ZuluSCSI and they said it should work fine. I might end up going that route.

Thanks for the info on the Floppy Emu, I just assumed since it does not work in HD20 mode with an accelerator that it was fully incompatible. I did not know it will still work in floppy mode.

 

[Phipli]

I don't know anything about this Performer clone, but is it supposed to work in a Mac Plus?

Generally you get away with using the patches from any similar accelerator with the same speed CPU because the revised timings are the same... But I think the Performer's original driver is available online. There are a few upgrades for the Plus and older. Total Systems made insane upgrades that would go in a 512k and add a fast 030, SCSI, RAM and even video out. Suspect you need the 512e ROM.

 

[cheesestraws]

ZuluSCSI ought to work, I'd expect. Its SCSI implementation is very similar to that from the last scsi2sds, and I personally haven't noticed any regression in compatibility across my Macs.

Be braced for needing to fiddle a bit, though: there are three revisions of the Plus ROM, each of which has its own distinctive weird quirks in SCSI implementation. You can really tell that the Plus was the first iteration of Mac SCSI, shall we say. So it won't necessarily be the case that a precise setup that works for someone else will work for you, regardless of what device you pick, unless you also have exactly the same ROM revision.

Also, the Floppy Emu is brilliant. I don't have an accelerated Plus but it works with all the other accelerated machines I've got. One of the absolute best "retro" purchases I've ever made. Thoroughly recommend if you're mucking about with more than just one machine.

 

[Phipli]

@bigmessowires @cheesestraws

I just had a thought.

I know some manufacturers didn't bother patching the HD20 timings with their accelerator drivers (SCSI was the thing in the 90s when most of the Accelerators were sold), but as I mentioned, most of the drivers "just work" with other brand upgrades, mostly. There are exceptions in how extended RAM, video and cache are implemented... But...

By this logic, we only actually need to find one manufacturer which bothered patching the HD20 timings for a few speeds, say 16, 25, 33 and 50MHz?

I wonder if any of them did? @Bolle? Any thoughts?

 

[bigmessowires]

Yes the HD20 routines would need to be patched. I have never looked at this, but the IWM or SWIM has its own clock which I'm assuming accelerators don't mess with, in which case the basic bit rate for reading and writing should be unchanged in an accelerated machine. When reading multiple bytes the driver code polls until the MSB is 1 for each byte, so there's already flow control that should work. When writing multiple bytes I can't remember how it works... I think there's a flow control mechanism but it might simply be a timed loop that would need adjustment for an accelerator. The bigger problem may be various busy-loop timeouts in the code.

 

[Phipli]

Yes the HD20 routines would need to be patched. I have never looked at this, but the IWM or SWIM has its own clock which I'm assuming accelerators don't mess with, in which case the basic bit rate for reading and writing should be unchanged in an accelerated machine. When reading multiple bytes the driver code polls until the MSB is 1 for each byte, so there's already flow control that should work. When writing multiple bytes I can't remember how it works... I think there's a flow control mechanism but it might simply be a timed loop that would need adjustment for an accelerator. The bigger problem may be various busy-loop timeouts in the code.

The Total Systems upgrades I like best actually start at a lower speed to maintain compatibility and only clock up to higher speeds once the control panel loads in the patches. I like their accelerators.

 

[JC8080]

I finally assembled my BlueSCSI v2 external drive and it works great with the accelerator.