Re: Looking for PDP
>glen herrmannsfeldt wrote:
> >email@example.com wrote:[/color]
>> I'm the program director for a non-profit in Colorado and I am looking
>> for a PDP-11 that we could use to train students with and to introduce
>> them to our beginnings. I know PCs are available for emulation and
>> used instead, but I was hoping someone may have a surplus, give away
>> PDP-11 or other mini-mainframe that we could pick up and cart away.[/color]
> There may be enough LSI-11 machines around that you might find
> one for a low price.[/color]
Jerome Fine replies:
In addition, if it is really important to run on an actual DEC PDP-11 CPU,
you may find that it takes more than one acquisition to acquire a complete
working system. Very often, after you find one portion of a system, other
parts will become available soon after.
As for using an emulator, I find that they run the software just as well as
the real PDP-11 hardware, but without all the difficulty of finding a
complete working system. So why not use a combination of both
types of hardware. One real DEC PDP-11 CPU along with an old
serial terminal such as a VT100 or a VT220 is probably sufficient to
demonstrate how a real DEC PDP-11 looks and feels, but I suggest
that only a few dedicated PDP-11 hardware addicts would insist on
a real DEC PDP-11 CPU all the time.
In that regard, SIMH is licensed to run up to V05.03 of RT-11 which
is available for download at:
The file RT11DV10.ISO.zip holds most of the RT-11 binary distributions
from V1-15 up to V05.03 of RT-11. bitsavers also has RT-11 manuals
available in PDF format.
Hopefully, hobby users will soon be able to use E11 as well to legally
run RT-11 and maybe somehow V05.07 of RT-11 will become legally
available to hobby users to run as well, although this situation has been
ongoing for MANY years and does not seem likely (i.e. with versions
of RT-11 after V05.03) to be resolved for another decade or two.
I find that the primary advantage of E11 (since I have a number of
legal RT-11 licenses that I can use) to be the built-in VT100 emulation
as well as the extra speed. E11 runs more than 100 times faster vs a
real DEC PDP-11/93 on a high end Pentium Quad CPU and the disk
I/O with SATA II hard drives is even faster.
So by all means have one demonstration DEC PDP-11 CPU. But if
you are attempting to demonstrate the software, I really can't see the
advantage of insisting on original hardware.
>> I'm not sure such a thing exists, but if I don't ask I'll never know
>> and it would be a great addition to our program if we could get one. I
>> used a PDP-11/45 when I worked for AT&T and thing if I could load an
>> OS and a compiler of some type it would be a great learning tool.
>> Almost anything with lights, tape deck, big disks and such would fill
>> the bill.[/color]
> Disks and tapes are more of a problem. With moving parts they
> tend to be less reliable. Floppies yes, but anything else will
> cause lots of problems if you do manage to find one.
> 8 inch drives aren't so hard to find, but HD 5.25 or 3.5in
> drives can be interfaced to an 8 inch controller, and will
> be much easier to find media for.[/color]
A word of caution. The 5 1/4" RD53 (Micropolis 1335) heads tend
to stick. Other hard drives are longer lasting. Personally, I use
Hatachi 5 1/4" ESDI drives on the real DEC PDP-11/83 CPU
in a BA123 box.
> 9-track tape drives will be expensive and lots of work.[/color]
The TK50 is too slow to be really useful. The TK70 is much
more reliable as well. Both use the same CompacTape I or II
media, although you MUST blank erase to switch from the
TK50 to the TK70. Both of these tape drives are 5 1/4"
and fit nicely into a BA23 or BA123 box. But they are not
very flashy and probably don't look much different from any
DLT tape drive.
> SCSI for Q-bus tends to be expensive, but would work with
> easily available drives. It shouldn't be hard to interface
> IDE/ATA to Q-bus, and not so hard to write the driver, either.[/color]
The drives tend to be VERY inexpensive (50 pin header with
separate power cable) at 4 GB or less. But a Qbus host
adapter (CMD CQD220TM) is still expensive.
> Anything other than an LSI-11 is probably too collectable
> to be given away[/color]
Not always true. I can't seem to find anyone who will pick
up any PDP-11 hardware in Toronto. I have enough BA23
boxes and boards to put together a number of working systems
Maybe next year I will drive to Ohio and sell a few of them.
> There are people interfacing front panels with lights and
> switches to emulators to allow the look and feel without
> the old hardware to keep maintaining.
> -- glen[/color]
Probably useful for the really addicted hardware types, but
a PDP-11/73 in a BA23 box has no lights or switches to
speak of and looks close enough to a PC (waiting for the
claims to the contrary) that a windows Dummy might not
even notice. The PC I use to run E11 is much taller than a
BA23 (24 1/2" high) and has TEN 5 1/4" full height bays
(well half height for an RD53 drive bay). I use three 160 GB
hard drives to hold all the files I want online. There is a SCSI
Adaptac 2940AU host adapter that I can use to run SCSI
hard drives from the real DEC PDP-11/83 just as they ran
on that system along with an Iomega SCSI insider or a Sony
SMO S-501 on the odd occasion when I want to transfer
files between to real DEC PDP-11/83 and what I run under
In summary, one real DEC PDP-11 CPU is nice to be able to
demonstrate the real DEC hardware for those who care. For
the software addicts (like myself - and there are probably no
others on this list), it does not seem to matter if I run under SIMH
or E11. The PDP-11 operating system (RT-11 in my case) is
what is important. I bit of a tired refrain - my goal is to enhance
RT-11 to allow dates up to the year 9999 CE or what I call Y9K
compliant along with other enhancements such as an LA: (Logical
Assigned Lookup List pseudo device driver) which acts like the
LNL (Logical Name List under VMS) or the PATH Name in DOS.