TK50 with SCSI

Ethan Dicks ethan.dicks at
Mon Apr 21 11:02:03 CDT 2008

On Mon, Apr 21, 2008 at 08:37:08AM -0700, silvercreekvalley wrote:
> Sorry if this has been asked before...

It has...
> I have a few spare TK50 drives, and wondered if
> these could be interfaced in some way to a regular
> Linux box. 

Do you have bare drives (as one would mount in a BA-23) or
external drives (as one would attached to a MicroVAX 2000)?
> I know the PDP's use a special interface card, but
> I seem to recall it was some kind of SCSI variant.

I don't know how the TQK50 might be thought of as a SCSI
variant, unless from a high-level design angle (perhaps).

> My reason for interfacing is that I have a few
> TK50's on PDP 11's and it would be useful to
> be able to transfer software.

If you have a bare drive, I don't know what to suggest
except to find the board from an external drive.

If you already have an external drive, I recall two
variants... the TK50Z-FA and TK50Z-GA.  The -FA and -GA
ROMs are different, but the internal drives are identical,
and the interface converter boards are quite similar.

The TK50Z-FA shipped with the MicroVAX 2000, and is nearly,
but not quite, SCSI.  I think the largest problem is sharing
the bus with other drives (but it could be more than that).
We had some limited success 20 years ago, hanging a TK50Z-FA
as a lone device off of an Amiga SCSI controller, if I am
remembering correctly.

The TK50Z-GA was *designed* to be a SCSI drive.  It has, I
think, a drive unit select switch of some sort, and _should_
play nice on a bus with other drives (can't be sure about
"disconnect" and bus blocking, though).

I have not tried it, but I understand that you can drop -GA
ROMs into an -FA and it will work as a -GA, but I don't 
think you can change the drive's SCSI address without some
board hacking.

Another alternative would be to find a TK30Z drive somewhere.
That should be a) more mechanically reliable than a TK50,
and b) ready to go in a SCSI environment.

If you wanted to read/write install tapes and such, a
TK50ish drive on a modern machine could be handy.  OTOH,
you might find that a spare serial port and KERMIT might
be easier to work with than hanging an ancient tape drive
on a modern machine, especially since the TK50 holds *at
most* 95MB.  With time and wear and tear, etc., even a
9600 bps serial line might seem fast.

Hope this helps clarify some of the details of TK50s.

Good luck with whatever approach you take.


Ethan Dicks, A-333-S     Current South Pole Weather at 21-Apr-2008 at 15:50 Z
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