Baydel Unibus disk systems

Mike Ross tmfdmike at
Mon Mar 21 23:45:09 CDT 2016

On Sat, Mar 19, 2016 at 9:41 PM, Christian Corti
<cc at> wrote:
> On Fri, 18 Mar 2016, Mike Ross wrote:
>> I just have the controller board; I don't have any of the hard drives
>> left. All I remember is the disk was an 8" and the interface is a
>> single 40-pin cable; so not SMD and not SCSI. Far too early for IDE or
>> ATA. Any suggestions for what the interface might have been and what
>> disks might have been used? What hard disks were around in late 70s /
>> early 80s that used a single 40-pin connector??
> My guess is that it's not a controller board but just the interface to the
> controller found in the external enclosure, probably with the hard drive.
> The interface would implement things like NPR and BR and the like, so there
> wouldn't be enough board space to implement a complete hard drive
> controller, especially if the board dates from that era. IMO it's something
> like a RX211 board for hard drives.

Well you were right on the money! I found a manual for the thing. More
precisely I found I had a manual for the QBus version of the thing
squirreled away.

Baydel called the entire Qbus subsystem the 'Baydel D405' - and Google
returns precisely zero relevant hits for that search! I don't know
what they called the Unibus version. The host interface (Unibus or
Qbus) was indeed only half the system. Bayel referred to it as the
'I-board' (for 'interface'); it talked via the 40 pin connector to the
'P-board' (for 'personality') mounted in the drive chassis; the
P-board did indeed implement the drive controller functions. The drive
was a Pertec D8000 20MB Winchester; the drive chassis could contain
one of these (which all my systems did) or two of these (which needed
a special handler for the OS) or one 20MB hard disk plus one Shugart
8" floppy - which emulated an RX02.

That all rings bells with what I had.

Doesn't help much as the chances of me finding such a subsystem are
tending to zero I suspect. But mystery solved!


'No greater love hath a man than he lay down his life for his brother.
Not for millions, not for glory, not for fame.
For one person, in the dark, where no one will ever know or see.'

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