11 Apr
2007
11 Apr
'07
8:37 p.m.
Subject: TU-58s (was Re: Some progress with my PDP-11/73 system)
From: "Ethan Dicks" <ethan.dicks at gmail.com>
Date: Wed, 11 Apr 2007 21:54:24 -0500
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
On 4/11/07, Jerome H. Fine <jhfinedp3k at compsys.to> wrote:
So happens one of my "small" pdp-11s uses a Tu58. the system is a BA-11V
with an 11/23 256k of ram, DLV11J and MRV11 rom(boot). Takes 10 minutes
to boot, setup VM: then copy key files to and reboot. After that it's
pretty decent even if I have to access a file on tape.
Everytime I runs it with a bunch of kids of the current PC generations
they go gaga and comment on how slow then I explain the amount of ram and
storage then they are amazed it can be a functional machine with so little.
They can't imagine a useful machine with 32kW of ram and 256kb of storage.
On the flip side I've used that same Tu58 to bring up iron that had no
removable storage. It's slow but very dependable.
Allison
But I once had a project that
used a real DEC TU-58. Not the fastest "random"
access device!!!!!!!!!!!!!!!!!!
They work better as "sequential" access devices - being long and thin
and travelling in one dimension, go figure. We used to optimize file
order on our console TU58s to speed up the boot times on our 11/725s
and 11/730s. Since the file order doesn't change, one just builds a
TU58 with EXCHANGE with each file following the other. The console's
8-bit-micro must cache the directory block, since the tape didn't whip
back to the start between each file.
Using unaltered console tapes from DEC resulted in, IIRC, about 15
minutes from turning the key to booting the hard disk. Replacing that
tape with one of our own devising shortened that pre-boot time to well
under 3 minutes.
I'd hate to rely on a TU-58 and no other block-addressable media on a
PDP-11, though. I survived a PDP-8 with a TD8E and TU56, but it was
somewhat tedious (cool to watch, though). TU-58s weren't as cool,
IMHO. 
5 Apr
5 Apr
1:35 p.m.
Allison wrote:
So happens one of my "small" pdp-11s uses a
Tu58. the system is a BA-11V
with an 11/23 256k of ram, DLV11J and MRV11 rom(boot). Takes 10 minutes
to boot, setup VM: then copy key files to and reboot. After that it's
pretty decent even if I have to access a file on tape.
Everytime I runs it with a bunch of kids of the current PC generations
they go gaga and comment on how slow then I explain the amount of ram and
storage then they are amazed it can be a functional machine with so little.
They can't imagine a useful machine with 32kW of ram and 256kb of storage.
Jerome Fine replies:
At some time or other, I saw a VT103 with dual TU-58
drives in the bottom. As noted, it took about the
lunch break to boot.
However, a VT103 can actually support a PDP-11/73
with all 4 MBytes of memory if the backplane is
upgraded to 22 bits. The other 2 quad slots can
have items like a TQK70, a DHQ11 and an RQD11-EC
which allows up to 4 * EDSI hard drives. In the
case of ESDI hard drives, I STRONGLY suggest
used a separate power supply. Otherwise, an
RQDX3 with an RD51 can also be used and it is
then possible to place the RD51 under the tube.
At that point, you can play games with those PC
generation of kids and tell that that you don't
even need a computer, just a monitor and keyboard!
If you use a dual PDP-11/73 or PDP-11/23 with a
DLV11-J (and no boot ROMs on the CPU), then
the SIGMA controllers are very handy, either
a dual MFM (or ESDI) version or the quad ESDI
version. Again, with the dual MFM version,
an RD51 (ST412) can be placed under the tube
and use the internal power supply of the VT103.
It must be about 20 years ago that I did this
conversion of the RD51 hard drive under the
tube. I think I still have the backup VT103,
but without any boards or a suitable controller.
With any ESDI drives, limit the use of the internal
power supply of the VT103 to a single drive for less
than 10 seconds which would probably be enough to
boot and copy any needed files to the VM: device.
Sincerely yours,
Jerome Fine
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12 Apr
12 Apr
2:06 p.m.
On 4/5/07, Jerome H. Fine <jhfinedp3k at compsys.to> wrote:
At some time or other, I saw a VT103 with dual TU-58
drives in the bottom.
I have one in the attic. I've never tried to boot from the TU58s, but
I have used them.
However, a VT103 can actually support a PDP-11/73
with all 4 MBytes of memory if the backplane is
upgraded to 22 bits. The other 2 quad slots can
have items like a TQK70, a DHQ11 and an RQD11-EC
which allows up to 4 * EDSI hard drives.
I've always wanted to load mine up like that - so far, all I've thrown
in there is a KDF11B, some memory, an RLV12, and a BDV11... not much
room left.
In the case of ESDI hard drives, I STRONGLY suggest
used a separate power supply. Otherwise, an
RQDX3 with an RD51 can also be used and it is
then possible to place the RD51 under the tube.
I'd still recommend an external PSU for any 5.25" disk. Perhaps if
you had a SCSI controller and 3.5" disk it wouldn't be bad.
At that point, you can play games with those PC
generation of kids and tell that that you don't
even need a computer, just a monitor and keyboard!
I think the whirring of the drive might give the secret away, that, or
the seek noises.
Still a fun trick to pull, though, presuming the audience has ever
seen a dumb terminal before.
-ethan
1 Oct
1 Oct
11:22 p.m.
Jerome H. Fine wrote:
At some time or other, I saw a VT103 with dual TU-58
drives in the bottom. As noted, it took about the
lunch break to boot.
At one point, I had a VT103 booting RT-11 from TU58 in about 30 seconds,
through judicious placement of the files on the tape...
Megan Gentry
Former RT-11 Developer
2 Oct
2 Oct
9:04 a.m.
I still have a small 11/23 in a BDV11-VA shoebox with a pair of Tu58s,
with 256k of ram it boots RT-11 in about a minute and longer (about
10minutes) from there to copy it to VM: and reboot from there to save on
running tape for small things.
If it took a luch time then the user never read teh chapter on using the
TU58 and there is a note on how to optimize that.
Allison
Megan Gentry wrote:
Jerome H. Fine wrote:
At some time or other, I saw a VT103 with dual TU-58
drives in the bottom. As noted, it took about the
lunch break to boot.
At one point, I had a VT103 booting RT-11 from TU58 in about 30
seconds, through judicious placement of the files on the tape...
Megan Gentry
Former RT-11 Developer
5699
days inactive
6238
days old
4 comments
5 participants
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