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Windows 9x CD-ROM device support fails with disks >= 256 MB #1556

@chschnell

Description

@chschnell

While trying to build a new Win95 image for v86 I noticed that the ATAPI CD-ROM support doesn't work.

As soon as the CD-ROM device is accessed I get blue-screens (recoverable) under Windows 95 like these:

Windows 95 example blue-screen screebshots Image
Image

Windows 98 fails silently without blue-screens, but in both cases the D: folder is completely empty.

I tried using:

  • the NEC CD-ROM driver from the Windows 95 boot floppy
  • the OAK CD-ROM driver from the Windows 98 boot floppy
  • the built-in CD-ROM driver of Windows 95 (which works under qemu, never tried it under v86)

Nothing helped, so I ran some more tests:

  • happens both at the v86 main site and with a local build of current v86 HEAD
  • happens both under SeaBIOS and Boch's BIOS
  • happens both in v86 debug- and release-mode
  • happens both using the Win95 and the Win98 image at the v86 main site (Win2K works)
  • happens using my own Win95 image with OAK CD-ROM driver, from here where I posted about having it working

I tried to fall back to the v86 repository state #1345 right when ATAPI CD-ROM support should be working:

git checkout d9088888e477663f0bf627a3e262d00af2849109

The problem was STILL there, that makes me doubt whether the released Win9x ATAPI support ever worked (what puzzles me is that I know that I had it working when I posted about it but now I can't reproduce it).

I can't remember if or when I last tested this after I had posted about it. Does it work for anybody else? Did it ever?

To summarize, CD-ROM support for Windows 9x appears currently broken, and it looks to me like it never worked.

EDIT: What does work is to boot from any boot floppy (Windows 95, Windows 98 or patcher9x) with a mounted CD-ROM image, I can access the CD just fine and run software from it.

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