New subject: BA11V

13 Apr 2007

...

Subject: Re: TU-58s (was Re: Some progress with my PDP-11/73 system)
   From: "Jerome H. Fine" <jhfinedp3k at compsys.to>
   Date: Thu, 05 Apr 2007 16:35:21 -0400
     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at
classiccmp.org>

 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. 
Files in wrong order.  I learned how to make a pdt11/130 
boot faster and thats a LSI-11 no extra ram.

One trick was to put bad blocks at the end of each track
to fource files to be sequential without wraping around 
to the beginning.  Saved a lot of long rewind/seek operations.

...
 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. 
A RX180 (VT180) disk box with a floppy and a 
st225 and a VT103, a sweet system with a 11/23 or 
faster CPU and 4mb ram (run VM:!)

...
 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. 
Sounds nice.  I have a few BA-11VA (four dual width slots)
and it's a challange to put enough boards to make a bootable
viable  sytem in that.  An 11/23, 256k ram, DLV11J and a Rom
card was full house and for storage the only choice was TU58
or Tu58 emulation (requires bukly balky PC).  Though at one 
time Sparetime Gizmos offered a TU58 emulator in hardware 
using ram with battery backup (total of 512k or DD0/DD1).  
I have one of them and that is remarkably fast as there are 
no seek dealys and at 31k baud you can move enough to 
appear decently fast.

There was also a third party TU58 like system that also 
used serial and instead of a tape it was rx50 compatable 
floppy.  I'd love to find one or at least drawings and rom 
code.

Allison

...
 Sincerely yours,

Jerome Fine
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