When I build a system, I usually make the CD-ROM drive drive letter something close to the end of the alphabet. Here are some notes from an old build:

Edit the AUTOEXEC.BAT file and make the following change: […]
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Edit the AUTOEXEC.BAT file and make the following change:

OLD: LH C:\CDROM\MSCDEX /D:MSCD000
NEW: LH C:\CDROM\MSCDEX /D:MSCD000 /L:Q

This change will make the CD-ROM Drive to be Q:. Reboot to enable the new drivers.

It's a no-brainer if you want to use an unused drive letter, but with your situation I'm not sure what would happen if you try to change the drive letter using MSCDEX. Did you try changing the drive letter to D:, i.e:

LH C:\CDROM\MSCDEX /D:MSCD000 /L:D

The load high (LH) is not absolutely necessary, and the designation after the /D is almost certainly something different for you.

use devload to load the aspidisk.sys from autoexec.bat or after mscdex has loaded and assigned a drive letter to the cdrom.

Gonduron wrote on 2021-12-31, 11:53:

System: - 486 with MS DOS 6.22 - Adaptec AVA-2825 SCSI controller - Plextor PX-83CS SCSI CD-ROM drive - Iomega ZIP-100 SCSI inte […]
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System:
- 486 with MS DOS 6.22
- Adaptec AVA-2825 SCSI controller
- Plextor PX-83CS SCSI CD-ROM drive
- Iomega ZIP-100 SCSI internal drive

Target:
Just for ease of mind, I would like to have drive letters assigned this way:
- Plextor CD-ROM drive on D:
- Iomega ZIP drive on E:

Problem:
- Right now, it's the other way round: CD drive gets assigned E:, and ZIP drive D:

Troubleshooting:
- In config.sys, the Adaptec ASPIDISK.SYS reserves drive letter D: for the ZIP drive
- In config.sys, the Adaptec ASPI2DOS.SYS does not reserve any drive letter for the CD drive
- Re-ordering those two lines does not help.
- In autoexec.bat, MSCDEX assigns drive letter E: to the CD drive

Question:
1) Is there a way to tell ASPIDISK.SYS that I want to reserve drive letter E: for the ZIP drive, not D:?
2) Is there a way to tell ASPI2DOS.SYS that I want to reserve drive letter D: for the CD drive?
3) Is there a way to create a dummy drive in config.sys, such as with the SUBST command (which unfortunately cannot be run inside config.sys).

Thank you for any hints 😀

EDIT: not sure what happened to what I typed, but basically I Was saying to load the Zip driver last...

That said, here is a quick rundown of the MSCDEX switches:

https://www.computerhope.com/mscdex.htm

Also, try loading the Zip drive driver last..

Also read up here, this may help, as I haven't done anything with Zip in a LOOOOOOOOONG time..:

http://www.geocities.ws/politalk/zip/index.html

akula65 wrote on 2021-12-31, 16:18:

It's a no-brainer if you want to use an unused drive letter, but with your situation I'm not sure what would happen if you try to change the drive letter using MSCDEX. Did you try changing the drive letter to D:, i.e:

LH C:\CDROM\MSCDEX /D:MSCD000 /L:D

I would imagine it will complain that the drive letter is already used by ASPIDISK.SYS given the current setup.

Maybe ASPIDISK.SYS has a parameter to let you set the driver letter?

weedeewee wrote on 2021-12-31, 19:37:

use devload to load the aspidisk.sys from autoexec.bat or after mscdex has loaded and assigned a drive letter to the cdrom.

FreeDOS's DEVLOAD does let you specify a drive letter explicitly, but just loading the drivers in the order suggested here should help.

Thank you for your suggestions. The FreeDOS DEVLOAD utility did do the job.

The challenge was to have the CD ROM drive on drive letter D:, which is reserved for the ZIP drive by ASPIDISK.SYS in CONFIG.SYS. Since no parameters are documented for ASPIDISK.SYS, you cannot assign it to another drive letter.

So I had to use DEVLOAD to load ASPIDISK.SYS in AUTOEXEC.BAT, in a line after MSCDEX.EXE has assigned the (still free) drive letter D: to the CD ROM drive. When looking for a DEVLOAD download, I first stumbled on the original DEVLOAD project (https://www.infradead.org/devload/) by David Woodhouse. Alas, the early DEVLOAD version does not allow to load high, so it is not applicable to my retro gaming machine, which I named "Pixeli" 😀 However, the later FreeDOS version (freedos.org) does load high, so problem solved.

Thank you!

Moved to Marvin -> Software.