DTC 520A - SASI or SCSI? - test-drb@ccmp.vtda.org

15 Dec 1999

Based on the names of most of the signals, I'd say the 50-pin host interface
connector is for an early version of SASI or SCSI but done tenuously enough
that there was margin for going with a standard when one evolved.  The
manual in my possession is dated January 16. 1980.  They didn't have a
standard then, and, in fact SCSI was still pretty much of an illusion at the
time.  I'd guess it's a safe bet that this one will work with SASI hardware
or even with some SCSI hardware.  I doubt that it will work with most
state-machine-driven interface devices, since some of the signals are not
present, and, frankly, this interface is far enough off the mark that it
probably needs a programmed I/O sequence to handle it.

Dick

-----Original Message-----
From: allisonp(a)world.std.com &lt;allisonp(a)world.std.com&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Wednesday, December 15, 1999 7:01 AM
Subject: Re: DTC 520A - SASI or SCSI?

...

Ok,

Likely that is something else.  I'd expect the 34pin to be floppy and
maybe MFM hard disk.

The 50pin could be... QIC02, QIC24 or maybe the old Hard disk interface
used for the 8" hard disks (SMD?) like the SA4000.

!983 SCSI ws likely SASI, but many tapes and disks used a 50pin parallel
like interface back then too.

Allison

On Tue, 14 Dec 1999, Ethan Dicks wrote:

>
> Going through a box of disk interface cards, I ran across a couple of these
...
 > DTC 520As.  Cursory examination shows a 50-pin
connector (J4) with two
> termination resistors (220/330), two 20-pin connectors (J2, J3) which are
> presumably analog data for two ST506 drives and two 34-pin connectors (J1
> and J9).  I would expect that J1 is the control cable that goes with J2 and
...
 > J3.  I suspect that J9 is for floppies.  The major
chips are two 8255s, one
...
 > 8085, one DTC-037, one NEC D765, one FDC-043, one
DTC MSA 2827G, an AMD P8353,
...
 > and an AMD AM9517.  There are several chips with
the numbers covered by type-
...
 > written numbers, PALs and ROMs, no doubt.
>
> There are 8 LEDs in a row by the power connector and an 8-position DIP switch.
...
 >
> >From the date codes, it appears to have been made near the end of 1983.
>
> Can anyone shed any additional light on this device?  Knowing what this was
...
 > expecting to hook up to and how to set the DIP
switches would be a great help.
...

 Many thanks,

 -ethan

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