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NCR DMV with Western Digital WD1001-05 ST506/MFM Board / Signetics 8x305 Controller


Jun 3, 2014
I have a 1982/84 NCR Decision Mate V (Five) in working order. That is, it boots from a floppy/gotek.

The base version uses a Z80 for CP/M-80 2.2. Among a variety of options were:
- an internal or external 8088 with which CP/M-86 and MS-DOS 2.11 were available
- an internal or external 10Mb ST-506/MFM hard drive.

My DMV has the 10Mb internal hard drive (an ST-412), which uses a 1982 WD1001-05 controller. The hard drive returns 'Not Ready' when accessed. Given that the two drives tested to date were functional when read with a David Gesswein 'MFM Emulator', I suspect there may be a fault with the WD1001-05 controller.

One reason for this suspicion is that there is a very incomplete install of MS-DOS on the ST412 drive. It's possible the controller may have failed at an early point in the install.

Here's a photo of the WD1001-05 board:

The WD1001 is well-documented. The hardware manual with schematics is on Bitsavers.org.

There are two initial steps that would be useful before deeper investigation:
- 'borrow' a WD1001 from another vintage system (early 1980s)
- replace the 50-pin socketed microcontroller on the board, a Signetics 8x305.

Can anyone help with information?
1. Which other systems used the WD1001-05 (or the WD1002-05 or WD1002-HD0)?

2. Which other systems used the 8x305 microcontroller?

Among the documentation of the DMV on oldcomputers.dyndns.org is a photo of the DMV's external (plug-in) hard drive interface. This shows a WD1002-HD0 controller board with a manufacture date of 1984. It seems possible that the WD1002 may have been fitted internally to DMV systems manufactured at a later date than mine.

Can anyone confirm whether the WD1002 is able to act as replacement for the WD1001?

With thanks in anticipation.


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Al Kossow

Documentation Wizard
Sep 1, 2006
Silicon Valley
If you should ever feel like desoldering the 82s181 parts I'd love to archive them.
As you can see on bitsavers, there were a couple of different versions of the 1001
all with different firmware.

There is actually someone currently working on a Motorola VME disk controller
for MAME that used the 8X305.

you can find some disassembled firmware here
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Experienced Member
Jan 10, 2012
jonhales a complete NCR DOS 2.11 should have two floppy disks, grab the disk packs from https://www.retroprograms.com/NCRDMV/dmv2.html
To format your HD, use "config" to set your system's disk configuration, you can choose between two 5MB partitions or one 10MB partitions - the scheme is quite inflexible.
As a treat I've included an alternative DOS boot disk that has a fmt20-5 command, which allows you to format a 615-4-17 size harddisk (think 20MB Seagates) to 20MB.
The commands to partition and format in one go are "format c:" or "fmt20-5 c:" respectively.

If you want a dry run to see what should happen, MAME's DMV emulation is quite capable.



P.S. As for your controller woes, the bus adapters for the internal and external harddisk kits use the same components, if you can find a WD1005-HD0 (iirc it's used in the Kaypro 10 as well), you should be good to go. I think it's a better idea to try different harddisks on your controller first, however. The MFM emulator is more of a recovery solution, so even if a drive can be read with it, it's not a given it'll work on the original hardware.
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