Clem and all
Your knowledge of this and many other obscure (and not-so-obscure) subjects
from the “early days” never ceases to amaze me. If only there was a way to
capture all these anecdotes into one coherent “Wikipedia of computing history”
… Many of these stories are absolutely fascinating, and often amusing too.
Whether it’s the “he did / she did *THAT* … (which still lives on today)” or
“we had to do this because of ” or “we cobbled this
together with a few parts lying around in the labs at ”,
they are great to read.
Keep sharing the stories ! Long live the glory days of computing !
Thanks
Jason A.
From: Simh [mailto:simh-boun...@trailing-edge.com] On Behalf Of Clem Cole
Sent: Thursday, 25 January 2018 6:44 PM
To: Mark Pizzolato
Cc: SIMH; Larry Baker
Subject: [External] Re: [Simh] VAX Tape Emulation?
On Thu, Jan 25, 2018 at 4:57 PM, Mark Pizzolato
> wrote:
I think the documentation comment “cannot write variable-length blocks and do
not allow skipping forward over records between read operations” was written
when talking about the common cartridge tapes that were available on 80s and
90s Unix workstations. I don’t recall the name.
That was not UNIX, that was the QIC standard. Yes, those were blocked at 512
bytes. Apollo's domain systems had a b*tch of time with them because their
standard disk block was 1056 bytes
These things only supported fixed block size operations and not variable
record lengths (i.e. 80 byte tape labels, then different sized data records,
etc.).
Right the 80 byte ANSI label, then different length data records. UNIX
handles that fine, even with RMT. FYI: My grad school housemate, Tom Quarles
(of SPICE3 fame) wrote the ANSI tape and bunch of other tape support that most
UNIX systems used, explicitly so he could read/write VMS tapes for the DEC guys
who were doing some of the funding of the USB CAD lab. Leffler (who wrote
rmt) used Tom's tape stuff for the original debug of rmt.
Given that the remote tape drive was a drive which could do variable length
record activities, I think MultiNet’s rmt support actually worked well. I
don’t remember testing it though. Whether someone should try to do that now to
backup simulated VMS systems is another subject I may write about a little
later.
Understood. I was just suggesting trying to keep another emulated system
out of the scheme and going directly to the remote device either through DECnet
or rmt or maybe even using a NAS as virtual tape files. It just seemed
running a Linux with a tape and then running an emulated VAX on top of that
seemed like an extra layer of indirection if there was an easier path.
ᐧ
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