[Info-vax] DLT drives and antique SCSI compatibility (was: Re: Next release of OpenVMS x86_)

[Stephen Hoffman]

On 2020-07-10 21:58:28 +0000, Terry Kennedy said:

> To comment on another reply, I was told by a reliable source that the 
> TZ30 was the result of a barroom bet between a DECie and a Mitsubishi 
> engineer about the impossibility of making a half-height DLT drive. 
> Despite the "Z" in the model name, it is *NOT* a SCSI-compatible 
> device. In fact, it can hang both halves of the only controller it was 
> every supported on, the RQZX1. Simple user mode I/O is sufficient.

That sounds... odd...

RQDX1 was MFM, and AFAIK was never used with a DLT.

DLT tapes were offered with the sorta-SCSI with the MicroVAX 2000 and 
VAXstation 2000 (TK50-Z, IIRC—the TZK50 was the intended-for-SCSI 
variant, IIRC), SCSI (TZ30, TZK50, TZ70, etc), DSSI (TF70, etc), and 
the earliest TMSCP-based TK controllers such as the TQK50 used with the 
TK50 and TK70.

The TK50-Z was the one most folks had issues trying to use else-platform, IIRC.

TZ30 was a half-height SCSI controller.  The TZ30 INQUIRY data was 
reportedly badly bogus (ASCII NULs?), in at least some of the firmware 
revisions. If not in all revisions. Returned identity data which then 
hosed compatibility.

Various SCSI hardware back then was somewhere between funky and 
mutually-incompatible, too. SCSI and ATAPI and USB and ilk are such a 
joy to work with.


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