OT: A call to arms (sort of)

From: Allison J Parent <allisonp_at_world.std.com>
Date: Sat Jul 3 08:47:00 1999

<> PDP-11 could be that architecture for several reasons:
<> 1) It has lots of software available for it.
<What it doesn't have is a free OS :-(.

Write one! However unix is $100 for the universal license (PUPs) and
it's not out of the question to port some other OS to it or even create
one. UZI unix kernel is for z80 but is small enough and written in C to
port to any of the PDP11s.

What make porting to PDP-11s more difficult is the devices (mostly tapes
and disks) are not always well enough documented (MSCP!) unless you find the
right book. However the RAW cpu is widely known. For those that would want
to play with PDP11 cheap find an old RQDXn controller and pull the T-11
chip. It's a 40 pin, 8/16 bit bus, PDP-11 that needed minimal glue
for ram, rom and IO.

<Does anyone know what DEC's restrictions are on these buses now? At one
<time they were patented by DEC, and you could only (legally) homebrew a
<certain number of cards per machine.

I thought copyrighted, and in either case for non commercial use it's
likely not an issue. Besides the CPU all you need is ram, rom, IO, storage
and for qbus thats totals 4 cards! With some of the 11/23B cards there is
2 serial ports and rom on the cpu so you only need ram and storage. Of
course a falcon (KXT-11) is complete save for storage with cpu, ram, rom
serial and parallel io and QBUS.

The Qbus, Omnibus are open and the specs for them were widely available
along with DEC even making WW boards for them. DEC also had some nice
chips to make the bus interface easier but Heath didn't use them in the
h11. its very common to find old machine with custom boards in them.

Received on Sat Jul 03 1999 - 08:47:00 BST

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