SCSI options for PDP 11/23

From: Pete Turnbull <pete_at_dunnington.u-net.com>
Date: Thu Feb 28 02:21:29 2002

On Feb 27, 20:49, Zane H. Healy wrote:

> OK, what I see that concerns me is the fact you're using a 11/03 box.
> Unless I'm mistaken the 11/03 was only Q16, which has me wondering how
> you're even running a 11/23 CPU, which should be Q18, in it (it's
possible
> someone upgraded the backplane to be 18-bit).

An 11/03 backplane is already 18-bit. BDAL16 and BDAL17 are bussed so it
can use parity memory.

It's also easy to upgrade to 22-bit, by soldering wrirewrap wire onto the
extra 4 lines, though any 11/23 or 11/23+ will work fine (as an 18-bit
system) without doing that. I can't think of anything that will fail to
work on such a system, apart from software that needs more than 124KW of
memory, obviously. Specifically, I/O page access will work coreectly for
any properly designed device, and RT-11, RSX-11, etc will just see it as a
normal 18-bit system.

Oh, and an 11/23 would work fine on a 16-bit backplane, unless you wanted
to use parity memory. The MMU wouldn't be useful (you could take it out,
though you don't have to; an 11/23 will work fine with 28KW and no MMU
chip).

-- 
Pete						Peter Turnbull
						Network Manager
						University of York
Received on Thu Feb 28 2002 - 02:21:29 GMT

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