DSD 880 Q Bus RL02 emulator

From: Jerome H. Fine <jhfinepw4z_at_compsys.to>
Date: Sun Apr 27 17:00:01 2003

>Don Mitchell wrote:

> I have a Data Systems Design DSD 880 Q-Bus drive.
> It dates from 1982 or 1983, and is a RL02 emulator (as I
> remember); there's a big old 8" drive (Shugart, I think) in
> a 19" wide rack mount. Also, there's a Q-Bus interface.
> The last time I used it was maybe 1985, but more likely
> 1984, and it worked. It could be set to look like an RL02
> with 5 mb but also you could set it up to give something
> like 7 or 8 mb, as I remember.
> A quick look in the old documentation box doesn't show
> anything there for it.
> I have no Q-Bus equipment on which to test it; I wouldn't
> bet on its working at the moment, but it might. Storage
> conditions have been, let's say, casual.
> I'd be happy to let it go for ACTUAL SHIPPING COST. It's
> located in Buffalo, NY.
> Don Mitchell

Jerome Fine replies:

You have what is called a DSD 880/8. You are correct as
far as the hard disk drive is concerned.

This drive is also quite heavy relative to the 8 MBytes of
capacity. I recommend local pickup. After the media
scare over SARS is finished by the end of April and the
WHO admits it made a mistake by the end of May, you
can come a pick up my DSD 880/8 in Toronto. I can
also provide a DSD 880/30 after I dig it out from the
pile. Unfortunately, both hard drives are no longer working.

It also contains a SINGLE 8" RX03 floppy disk drive. The
RX03 is compatible with the DEC RX02 floppy disk drive,
which is both a SSDD (Single-Sided Double Density) and a
SSSD (Single-Sided Single Density identical to the IBM
8" SSSD floppy disk drive media) when ONLY one side is
used. The RX03 can use both sides in either Single Density
or Double Density mode. As a result, when the appropriate
device driver is available, the RX03 can hold up to 1976 blocks
as opposed to only 988 blocks for the RX02 and 494 blocks
for the RX01 (always only SSSD).

The reason I know it is possible is that I also have a broken
DSD 880/8 along with a probably broken DSD 880/30.
The latter has the same RX03, but the hard disk drive emulated
3 * RL02 hard drives or 30 MBytes in total.

NOTE: The DSD 880/8 and the DSD 880/30 can handle
only 18 bit addresses on the Qbus. If the device driver in RT-11
is the standard one distributed from DEC, then there is no
provision for 22 bit buffer addresses. However, I managed to
modify the DYX.SYS device driver to handle BOTH the
Double-Sided RX03 and 22 bit addresses, the latter with
a bounce buffer within the device driver. Since at one
point I used the RX03 as my primary backup device, having
1976 blocks with the RX03 as opposed to only 988 blocks
with the RX02 was a big advantage.

Sincerely yours,

Jerome Fine
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Received on Sun Apr 27 2003 - 17:00:01 BST

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