Very interesting device! I didn't know these existed.

So MCDDRV.SYS is a modified version of OAKCDROM?

Did you try VIDE-CDD and MSCDEX to load it as a single drive to see if it works?

NEC_IDE.SYS is the modified Oak driver. MCDDRV.SYS is a very tiny driver (1KB only) so it cannot be a standalone CD driver. It must be an augmenting driver specialized only to do one thing.

You can use other IDE drivers, and indeed they will only recognize a single drive letter (I tried a stock Oak driver and UDVD2.SYS). But MCDTRAY.COM still refused to operate, so I'm guessing it is trying to communicate with MCDDRV.SYS but not finding it loaded.
Not sure what MCDDRV.SYS is looking for in this case. Is there a way to disassemble .SYS files? Maybe something interesting will show up there.

wbahnassi wrote on 2024-09-09, 11:35:

NEC_IDE.SYS is the modified Oak driver. MCDDRV.SYS is a very tiny driver (1KB only) so it cannot be a standalone CD driver. It must be an augmenting driver specialized only to do one thing.

You can use other IDE drivers, and indeed they will only recognize a single drive letter (I tried a stock Oak driver and UDVD2.SYS). But MCDTRAY.COM still refused to operate, so I'm guessing it is trying to communicate with MCDDRV.SYS but not finding it loaded.
Not sure what MCDDRV.SYS is looking for in this case. Is there a way to disassemble .SYS files? Maybe something interesting will show up there.

This is a translation from an old Hungarian-language forum - does it make any more sense to what you're seeing...

> I had DOS drivers on the "factory" disk, only install.exe wanted
> windows on everything. With the installer (3 files need to be loaded,
> install also does this):
> in CONFIG:
> DEVICE=[...]\NEC_IDE.SYS /D: NECCD -> assign 4 letters to the drive, or
> DEVICE=[...]\MCDDRV.SYS /D: NECCD -> assigns 1 letter to the drive
> (The install puts _both_ at the same time, re-locks one, and
> you can recall the install in Windows (called CD Changer setup utility), which
> puts the REM in config.sys there (!!! 😀 and says to reboot...)
>
> in AUTOEXEC:
> [...]\MSCDEX .EXE /D: NECCD
>
> If there is a letter (MCDDRV.SYS):
> [...]\MCDTRAY.COM {drive letter} {tray number} is replaced at any time
> (slotutil.exe does the same from Windows)

Thanks. This confirms my expectations on how the driver is to be used. I'll give it another try to see of I can convince it to work. Maybe try it on another system.

I feel this "single drive mode" makes most sense to me. In multi drive letter mode, you need to remember from which try you installed your game, as it will always look for that specific drive letter when running.

Got it to work!

I don't know about that old mailing list post, but my version of MCDDRV.SYS won't work unless you specifically use the name "MCHGR_01" for the device. I found out this name by looking at the driver's binary data. So, here is my documentation on how to setup this drive:

1- Multi-drive mode:
In CONFIG.SYS:
DEVICE=C:\CDROM\NEC_DRV.SYS /D:MCHGR_01

In AUTOEXEC.BAT:
C:\DOS\MSCDEX.EXE /D:MCHGR_01

The above (with the right modded NEC_DRV.SYS file) will result in 4 drive letters added to the system. Each maps to one of the drive's trays.

2- Single drive mode:
In CONFIG.SYS:
DEVICE=C:\CDROM\NEC_DRV.SYS /D:MCHGR_01
DEVICE=C:\CDROM\MCDDRV.SYS /D:MCHGR_01

In AUTOEXEC.BAT:
C:\DOS\MSCDEX.EXE /D:MCHGR_01

The above will result in just one new drive letter, even if NEC_DRV.SYS is reporting 4. MCDDRV.SYS will take over the 4 and virtualize them behind a single drive letter. Now, after a restart, the CD drive letter will always map to tray 1. To remap the drive letter to another tray, run:
MCDTRAY.COM 2
The above remaps the CD to tray 2 ..etc. Now when you access the CD drive, the drive will switch to tray 2 and give you the contents of that CD.

Notes:

• MCDDRV.SYS loads successfully with other drivers than NEC_IDE.SYS (e.g. UDVD2.SYS), but you always get "CDROM Not Ready" error when trying to access the drive. So just stick to the changer-mod version of NEC_IDE.SYS.
• MCDTRAY.COM can be used to eject/retract the trays, but I found it a bit dumb. Once the tray door is open, it just refuses to do any operation until you close the tray yourself using the chassis buttons.
• It would be VERY cool if MCDTRAY.COM was a TSR that monitors key combos (e.g. CTRL+F1/F2/F3). This would allow switching CDs in those multi-CD games (hello Phantasmagoria) without leaving the game. Too bad NEC hasn't explored this opportunity.

Well, now I really like this drive 🤩 Single-drive mode is what I assumed a CD changer always operated as.

Thank you for documenting this! Now I have finally been able to set mine up to work as intended in DOS.

I'm sure the multi drive mode is for multi cd games which let you pick unique drive letters for each disk to eliminate swapping

I’m just using the single drive mode and it works great. I can actually store 4 CD’s now and switch to them in Dos.

Yeah it's cool. But if you're in a multi-CD game like Phantasmagoria or Gabriel Knight 2, the game will eventually ask to change the CD from within the game. You can't bail out to DOS to run MCDTRAY.COM at that point. I would love to reverse-engineer MCDTRAY.COM and write a TSR that supports keyboard shortcuts such that I can press ALT+F1/F2/F3/F4 to change the CD while the game is still running.

Alright, back once more into this topic. I did an analysis on how MCDTRAY.COM works, and it turns out it's quite simple, so I took that mechanism and put it behind a TSR that allows changing the active tray using keyboard shortcuts. The full DOS driver package is attached, and includes my new tool MCDKEY.COM. It is a super tiny TSR and can be loaded high, so shouldn't be trouble really. I wish I could incorporate it directly into MCDDRV.SYS, but I'm not in the mood for a full reverse-engineer like that.

To use this, simply add it to AUTOEXEC.BAT after MSCDEX.EXE is loaded. The keyboard shortcuts are then: CTRL+F1, CTRL+F2, CTRL+F3, and CTRL+F4. If you got the TSR loaded right, you should hear a tone following each of the commands. They are assigned to major-scale notes on the PC speaker, so you can tell from the key press which tray was selected (well, you'll need some ear training, but hey).
Like MCDTRAY.COM, the actual tray swap happens on the next CD access, so you can quickly change between any of the trays while CD access is off.

Tested this with Wing Commander IV and Phantasmagoria 1.. both work great.. Phantasmagoria sometimes shrugs after the tray change happens mid-game, and needs you to click "Retry" to access the CD again. It works fine afterwards... I don't think that is something that can be improved via MCDKEY.COM nor MCDTRAY.COM.

You can use the /Q switch if you don't like seeing the loading message (I'd put this if loading the tool via AUTOEXEC.BAT).

Enjoy!

I am so happy I found this thread. I had the privelege of owning one of these drives, purchased in early 1996. My uncle bought Phantasmagoria in late 95, we had a 2x single drive, and he went out looking for a faster drive. Well he found this NEC 4x4 cd changer, and it solved two problems, it was the solutuion to having to change the disks manually.

This particular piece of old tech is something I wish I had never parted with. I have spent the better part of 25 years, watching ebay, searching globbaly tryng to track one down at a resonable price, hoping to one day get my hands on one again. I am happy to report that day has finaly come! I scored an amazing deal on a unit from ebay, and it arrived today. Power on test passes, and it will take 4 disks, I feel like a kid again.

This is the second to last piece I needed to complete my 486 retro build that matches my exact system as it stood in early 1996, a AMD 486 DX4-120 with 32mb of ram, Soundblaster AWE32 sound card running windows 95, aaaanannnndddd this awesome NEC Multispin 4x4 cd-rom. It really feels like christmas, and I know my uncle would be so happy if he were here. Thanks to your write up and shared drivers, I will have this up and runing in no time. I already have Phantasmegoria out and ready for a playthrough.

Now I just need a Diamond Stealth 64 VLB video adapter to complete it, I am still running on a Matrox Millenium 4mb. One step closer to completion..............

wbahnassi wrote on 2026-07-10, 21:23:

Alright, back once more into this topic. I did an analysis on how MCDTRAY.COM works, and it turns out it's quite simple, so I to […]
Show full quote

Alright, back once more into this topic. I did an analysis on how MCDTRAY.COM works, and it turns out it's quite simple, so I took that mechanism and put it behind a TSR that allows changing the active tray using keyboard shortcuts. The full DOS driver package is attached, and includes my new tool MCDKEY.COM. It is a super tiny TSR and can be loaded high, so shouldn't be trouble really. I wish I could incorporate it directly into MCDDRV.SYS, but I'm not in the mood for a full reverse-engineer like that.

To use this, simply add it to AUTOEXEC.BAT after MSCDEX.EXE is loaded. The keyboard shortcuts are then: CTRL+F1, CTRL+F2, CTRL+F3, and CTRL+F4. If you got the TSR loaded right, you should hear a tone following each of the commands. They are assigned to major-scale notes on the PC speaker, so you can tell from the key press which tray was selected (well, you'll need some ear training, but hey).
Like MCDTRAY.COM, the actual tray swap happens on the next CD access, so you can quickly change between any of the trays while CD access is off.

Tested this with Wing Commander IV and Phantasmagoria 1.. both work great.. Phantasmagoria sometimes shrugs after the tray change happens mid-game, and needs you to click "Retry" to access the CD again. It works fine afterwards... I don't think that is something that can be improved via MCDKEY.COM nor MCDTRAY.COM.

You can use the /Q switch if you don't like seeing the loading message (I'd put this if loading the tool via AUTOEXEC.BAT).

Enjoy!

Thank you for this!! This helped me as well.

Might you know whether these files will work with a "Multispin 4Xc" 7-disc changer?

It's an external SCSI-based model I recently re-discovered, and I currently have cables on order to see if it still works.

Lylat1an wrote on 2026-09-15, 03:58:

Might you know whether these files will work with a "Multispin 4Xc" 7-disc changer?

It's an external SCSI-based model I recently re-discovered, and I currently have cables on order to see if it still works.

If it was IDE I would have said there is a high chance, but SCSI... you'll need to find its original driver pack first. If it also has the same MCDTRAY.COM as the 4x4 then you're in luck for MCDKEYS.COM.

Hmmm... was looking at LGR's video on the 4xc, it uses a different driver set than the IDE 4x4. One thing I noticed at https://youtu.be/z6HfEgCbMb0?t=8m43s is the Corel SCSI disk has a CDCHANGE.EXE program that I bet is for the same purpose as MCDDRV.SYS, to lump the drive letters into one and change the active disc via command line. Who knows, it might support keyboard shortcuts as a TSR as well.. Give it a try once you get your drive setup.

wbahnassi wrote on 2026-09-15, 14:23:

Hmmm... was looking at LGR's video on the 4xc, it uses a different driver set than the IDE 4x4. One thing I noticed at https://youtu.be/z6HfEgCbMb0?t=8m43s is the Corel SCSI disk has a CDCHANGE.EXE program that I bet is for the same purpose as MCDDRV.SYS, to lump the drive letters into one and change the active disc via command line. Who knows, it might support keyboard shortcuts as a TSR as well.. Give it a try once you get your drive setup.

Will do, thanks!

In the mean time, I found the software's manual:
https://archives.oldskool.org/pub/drivers/Cor … 20Materials.pdf

The manual shows how to setup the driver to assign only one drive letter to the CD instead of 7. Later it shows how to use CDCHANGE.EXE to change the slot to use for the single drive letter setup. CDCHANGE.EXE is similar to MCDTRAY.COM in its result, but the details are different of course.

If the Corel SCSI driver works on the 4xc, then we can explore building a TSR version of CDCHANGE.EXE, though it will be more difficult because I don't have the hardware (SCSI nor the 4xc).

wbahnassi wrote on 2026-09-16, 03:41:

If the Corel SCSI driver works on the 4xc, then we can explore building a TSR version of CDCHANGE.EXE, though it will be more difficult because I don't have the hardware (SCSI nor the 4xc).

If you're willing to try I don't mind assisting.

l'll see if my hardware works first, then possibly get back to you once the correct cables arrive.