Snow EMU - Emulator for 680x0-based Macintosh computers

PL212

Tinkerer
Dec 25, 2022
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I am, I think:

Screenshot 2026-09-15 at 1.19.17 PM.png


But the vendor is still SNOW:

Screenshot 2026-09-15 at 1.20.28 PM.png
 

PL212

Tinkerer
Dec 25, 2022
64
41
18
My host machine is actually Golden Gate, as of today.
The emulated machine is a IIcx with a Toby cared running System 7.1, installed from the Apple Mac OS 7.1 MultiPack CD-ROM, which is the third download on that page.
For CD images, I've tried a few dozen ISOs and Bin/Cues, drawn from the Nautilus collection on the Garden. All of the ISOs validate in DiskJockey, at least. (The Apple 7.1 CD itself also fails to mount, for what it's worth.)
The CD-ROM extension is from the installer Apple included on that CD-ROM, version 4.0, which is available in this path:

System 7.1 CD-ROM/U.S./Administrator Tools/Disk Images/CD Setup Disk/CD-ROM Setup.image


Screenshot 2026-09-15 at 3.57.31 PM.png


I've also tried the 'hacked' version the driver on the Garden, which allegedly removes all vendor checks:

Screenshot 2026-09-15 at 4.00.20 PM.png


I also tried FWB CD-ROM Toolkit 1.0 and 2.0; the former fails silently and the latter declares the drive to be unsupported. (Wonder if it's the vendor string there as well?)

I did triple-check that Snow had local disk permissions -- it happily mounts .hda and floppy images from the same folder...
 

eric

Administrator
Staff member
Sep 2, 2021
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MN
bluescsi.com
I dug into this with Snow's SCSI trace and the 4.0 driver.

Apple CD-ROM 4.0 (DRVR 32 ".AppleCD", from CD-ROM Setup.image on the 7.1 CD) checks two things when it probes a drive:

1. MODE SENSE page 0x30 has to come back with 'APPLE COMPUTER, INC '.
2. The 16-byte INQUIRY product field has to be one of exactly three strings: CD-ROM CDU-8001, CD-ROM CDU-8002, CD-ROM CDU-8003. They are at offsets 0x47FC, 0x480E and 0x4820 in the DRVR

Snow reports CD-ROM CDU-8004. That model only shows up in the later 5.x driver, whose table added 8004, 8005, CR-8004 and CDR-8004. So 4.0 rejects the drive.

I reproduced it in Snow on a IIcx with the real System 7.1 CD as the media:

- 7.0.1 + Apple CD-ROM 4.0, product CDU-8004: doesn't mount.
- 7.0.1 + Apple CD-ROM 4.0, product CDU-8003: mounts.
- 7.5.3 + Apple CD-ROM 5.3.1: mounts either way.

CDU-8003 is in both extensions - fixed here: https://github.com/twvd/snow/pull/371
 
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PL212

Tinkerer
Dec 25, 2022
64
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Fantastic -- checked out from your PR and:

finder.png
getinfo.png


Thanks for both the fix and explaining how you researched it. I'd never played around with the Peripherals or Breakpoints windows before; I'm guessing you knew enough about SCSI to know what to monitor?