13 Apr
2013
13 Apr
'13
5:56 p.m.
William Barnett-Lewis wrote:
I've been learning about the PDP-11 lately thanks
to the wonder that
is Simh, running various software on it and generally having fun. I
don't have any purpose other than that at this time. I've been running
everything I can get my hands on though I find, given my background,
tastes and biases, that it's usually either Unix Version 7 or,
especially, 2.11BSD that I'm firing up and exploring rather than, say
the more DEC traditional RSTS/E.
That said, I've been wondering what would be different (aside from
noise & heat ;) about running 2.11BSD on hardware rather than in Simh
on my increasingly decrepit Dell C640 running Xubuntu. Logically I
should spend the money on a new intel based laptop but what's the fun
in that?
If you don't already have any DEC systems to run 2.11BSD, then
I suspect that staying with SimH is probably a better alternative.
On the other hand, if you want to consider executing even faster,
Ersatz-11 makes a HUGE difference. While I the only comparison
I have is using RT-11, a reasonable estimate using current mutli-core
CPUs of more than 3 GHz running a Windows operating system such
as Windows XP or Windows 7 (which supports caching of the disk
drives) is about 150 times a PDP-11/93. The disk I/O will be even
faster In addition, Ersatz-11 supports VT100 emulation of up to 12
"terminals". If you need any additional information, please ask.
But then that turns on the question - is there even a
cheap PDP-11
that can run 2.11BSD? I don't need a speed demon but how small is too
small vs big enough?
Is there any particular reason that real DEC CPUs are important?
Let me see if I understand correctly what I would
need:
A BA23 or BA123 chassis. Would others work as well?
A CPU with separate I/D space. 11/23, 11/53, 11/73, 11/83 or 11/93
would work with the Q-bus chassis above.
A PDP-11/23 does NOT support separate I/D space. The J11 CPU
chip would be required.
1mb to 4mb memory, 1mb is absolute minimum for 2.11 BSD
& 4mb is
highly desirable.
Both SimH and Ersatz-11 will always provide 4 MB just bt asking.
Disk controller - though more expensive, sanity really
says I should
find a SCSI controller like RQZX1, Emulex UC-7 or CMD CQD-220. I have
old SCSI disks; ESDI & the like? Not so much ...
A RQDX3 & RX50 or TQK70 & TK70 would probably be in the 'nice to
have' category as well.
Under SimH and Ersatz-11, you also have access to much more "disk"
space. But you already know that.
DELQA ethernet controller
I don't use ethernet myself. How well does SimH handle ethernet?
Would this work? What are the going rates for hobbyists
(rather than
resellers to those with production equipment)? Are there any, hmm,
less expensive bits here or there?
A PDP-11/73 system in a BA23 box may still be available
free, but not in all areas of the US. Outside the US, they
are probably less available.
This is mostly a thought experiment as I don't
really have the
disposable cash right now for the various parts right now. OTOH, I
find the process of learning more about the hardware, what would be
required and how it functions, to give me a better understanding of
what I'm doing with the emulator.
In general, my experience with RT-11 under Ersatz-11 is that
the ONLY difference is that it is faster and more convenient,
especially the size of disk storage. On my real DEC PDP-11/83,
I have 4 MB, 3 * 600 MB Hitachi ESDI hard drives and SIX
VT100 terminals on the desk. I am still running Ersatz-11 under
Windows 98SE on a 750 MHz Pentium III with 768 MB of
memory. I have a Q9600 core-2 quad system with Windows XP
waiting to be upgraded, but there does not seem to be any real
incentive.
Thanks to all here (the 11/23 thread has been of great
value to me)
and to bitsavers ;) and all the other fun resources out there.
If you also try out Ersatz-11, I would be very interested in how
much faster it runs than SimH in addition to other aspects.. Please
let us know.
Jerome Fine