ajp166 at bellatlantic.net
Thu Nov 17 10:23:43 CST 2005
>Subject: Re: Minix
> From: woodelf <bfranchuk at jetnet.ab.ca>
> Date: Thu, 17 Nov 2005 08:31:01 -0700
> To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>>Minix on PDP11, Not that I know of. It would be interesting.
>Well I think Minix #1, would be easy to port, but why? You got real unix.
>It just proves how effective code on the 11 could be. Too bad you can't buy
>a pdp-11 cpu chip for $2.49 like a 8088. I take it is still rather pricy
>to put together a basic 11. Any body know how much?
If you can find a defunct VT240 or 241 box the CPU in there is T-11 (40 pin
basic PDP11) which was used on the Falcon card. I'd bet a DC310 can be had
cheap if you can find a source.
For PDP11s there are three catagories. Unibus machines, large and more
complex. Qbus machines (11/03, 11/23 series) smaller more common and
easier to work with. Packaged system PDT11/150 (11/03 with 2 8" floppies)
or Pro3xx (11/23 or J11 chips with floppy and hard disks). The PDT11/150
if could is a compact system and removes hardware from the picture as its
a bounded system. The PROs are bounded but do have option boards. The
Qbus systems are most often seen un bounded PDP-11s and are easily
The last 3 PDP-11/23s I got were free as in "Here, take it".
However if you want a SCSI card or maybe any disk controller those can
be harder as those are most often first things stripped.
For example I found a microPDP11 with the disks removed as they were MFM
and fit PCs of the day. The RQDX controllers are often stripped for Qbus
VAXen (microvaxII). Larger disks are like RL02 or RX02 get seperated and
"lost" or rescued in preference to the whole system.
But a basic box, cpu, memory and serial cards are common and cheap to
free. A PC with the right code can simulate TU58 tape and provide a
working system that runs RT-11. With a bit of creativity and a Qbus
parallel IO card and the PCs infamous and useful printer port a faster
parallel disk simulation is doable. Most small PDP11s (11/03, 11/23, 11/23b)
have ODT (Octal Debugging Tool) in microcode or local rom so a terminal
can be your front pannel making it easy to load a small boot program.
If that weren't enough there are a pot load of PDP11 sims that you could
develop on till hardware lands on you.
Now Minux on PDP11. Minix is not unix, the look to the user the same
but internally there is almost no commonality. Unix on PDP11 requires
a disk and later versions require the bigger/later 11s that have I&D.
Minix once loaded is entirely memory resident and uses relatively
small space for itself. For PDP11 I'd expect a 8kW version that runs
useful stuff in 24kW (pdp11s without MMU (LSI-11 [11/2 and 11/03]) would
not be out of the question due to code efficientcy of the -11. If later
CPUs (11/23, 23b, 73 for Qbus) are used then 256kb or 4mb are possible
with MMU. An -11 with 256k is a very repectable machine running any OS.
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