Re: KA410 Boot Failure With TKZ-50

[Johnny Billquist <bqt%update.uu.se@localhost>]

On 2020-06-14 04:15, Thor Lancelot Simon wrote:
> On Sat, Jun 13, 2020 at 10:29:06PM +0000, Josh Moyer wrote:
> > I wasn't asking if I should implement TMSCP, but rather whether my hardware
> > and firmware do.  I have a hunch that booting from MUA0 is breaking because
> > of the SCSI board in the TKZ-50, but I can't be more specific and could
> > easily be wrong -- it's just a hunch.
>
> This seems very unlikely.

Agreed.

> The TK50 hardware implemented neither TMSCP nor SCSI.  It implemented a
> very minimal proprietary protocol over a very, very slow serial connection
> (200Kbit/sec) to one of two possible controller cards: the SCSI TKZ50 or
> the QBus TQK50.  An 80186 (I think; might have been an 8085) on the
> controller card interfaced to one of the two possible host buses.

The TQK50 sits on the Qbus, and talks the serial protocol/interface you 
mention. My brain says "KLESI", but I could be confused.
There was also the TUK50, which was a Unibus controller for the same 
interface. And yes, both of these controllers have an 80186, and to the 
machine they present a TMSCP API.

The TKZ-50 have a daughterboard on the tape drive itself, which converts 
between SCSI and KLESI, so the tape drive have a standard SCSI interface.
From my recollection, that SCSI was a bit weird, so it could sometimes 
look a bit funny connected to generic SCSI controllers, but it usually 
worked fine.

> Unless your machine has Qbus slots, it's not going to be expecting to talk
> to a TMSCP TK drive.  And if you have a KA410, you don't have Qbus slots,
> you have a MV2000/VS2000 just like the one they plunked down on my desk
> on my first day at work at DEC in 1990 (they'd ordered me something nicer,
> but it didn't show up for several months).

And TMSCP tape drive is a bit of a misnomer. No drive that I am aware of 
talked TMSCP. The controller did, towards the CPU. Towards the tape, you 
might have had KLESI, SCSI, STI, or some other protocol/interface. TMSCP 
is a rather high level protocol/interface.

> I booted and installed Ultrix (probably 3.1) on that machine from a TK50
> connected with a SCSI cable, so you ought to be able to do what you're
> trying to do.

Agreed.

> That said, the TK50 hardware was OK but the tapes themselves did not
> have a stellar reputation for durability, so you may have trouble finding
> media good enough to use, at this point.  For years I had personal files
> backed up on TK50 so I kept an old DLT drive with DEC firmware around to
> ensure I could read them; I threw the DLT drive out when the TK50 tapes
> degraded so badly they would no longer read.

My experience, as well as that of others I know, is the exact opposite. 
The tapes are ok, but good luck finding a drive that works. Especially 
the early TK50 drives are absolutely horrible.
But even later ones are usually a headache. Open them up and clean them 
for a start. That is almost mandatory.

I regularly had to do that to a TK50 I was responsible for that was 
hooked to a VAX-11/750 while I worked at DEC.

I have several drives nowadays, but I usually just put them away. If I 
can get my hand on a TK70, it's much better.

> P.S. Here's something I can't remember, quite.  The KA410 also has an
> onboard controller for an ST506 hard drive.  Does _that_ emulate MSCP?

My recollection says that the whole disk format was done in software, to 
be compatible with the RQDX3. And looking in NetBSD, it looks like it 
has a simpler interface than MSCP for the disks on that controller. (But 
I could be looking at the wrong thing...)

  Johnny

--
Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol