4 Dec
2009
4 Dec
'09
7:31 p.m.
Just to expand slightly on Dave's concise response and avoid further churn: the PDP-11
departed from the earlier practice of special I/O instructions and implemented memory
mapped I/O. The top 4 kW is reserved for I/O devices, with a special signal being
generated on the LSI-11 bus that 'enforces' this. So a PDP-11 without memory
management will allow up to 28 kW; an 18-bit bus will allow up to 124 kW. I'll let
you do the math for a 22-bit memory management system.
I'm glad things are coming together! Cheers -- Ian
________________________________________
From: cctalk-bounces at classiccmp.org [cctalk-bounces at classiccmp.org] On Behalf Of
Dave McGuire [mcguire at neurotica.com]
Sent: Friday, December 04, 2009 2:57 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Reanimating a PDP-11/23
On Fri, December 4, 2009 5:52 pm, Pontus wrote:
4K for the I/O page..
-Dave
--
Dave McGuire
Port Charlotte, FL
Then, assuming
the cable really is correct (have you tried swapping Tx
and Rx?), is plugged in to the correct
This was the somewhat obvious error I
missed when checking the cable. I
discovered it by trying another cable which isn't keyed. So I
accidentally put it in upside down, which incidentally flips Tx and Rx.
Thanks for putting up with me :)
So now I get this:
28
START?
Which confuses me, I have a 32kB (or is it kW ?) worth of memory
installed (M8044-DD) configured to start at address 0. Shouldn't it say
32 instead of 28? How does the memory detection work anyway?