From: jnc@mercury.lcs.mit.edu (Noel Chiappa)
To: tuhs@minnie.tuhs.org
Cc: jnc@mercury.lcs.mit.edu
Subject: Re: [TUHS] Fwd: Choice of Unix for 11/03 and 11/23+ Systems
Date: Wed, 30 Sep 2020 13:58:17 -0400 (EDT) [thread overview]
Message-ID: <20200930175817.4575B18C0B2@mercury.lcs.mit.edu> (raw)
> From: Paul Riley
> Can you clarify something for me regarding memory? I understand the
> bottom area of memory in a Unix system is for the Kernel and it's stuff,
> and that the top 8kB is set aside for device I/O
Well, technically, the top 8KB of _address space_, not of memory - it's mostly
used for device registers, etc. Here:
http://gunkies.org/wiki/Unix_V6_kernel_memory_layout
is a bit more detail on how the memory is laid out.
> The LSI-11 board has 4kW of RAM on it, and I have already a 16KW
> board. If I want to further expand the RAM, and say I buy another 16kW
> board, that makes an arithmetic sum of 32kW for the boards, making 36kW
> total. Can the 4kW of on-board RAM be disabled, and only the 32kW on
> the boards be used?
Yeah, if you look at LSI-11 documentation, there are jumpers that allow
configuration of the on-board memory. Depending on the etch revision; for my F
revision, jumper W11 (at the top, towards the handle edge, in the middle of
that edge; just below the W1/W2 jumper pair) should be out to disable the
on-board memory.
Or you could configure the two 32KB boards to be at 020000 and 0120000; there
will be 72KB of memory total on the QBUS, but the LSI-11 CPU (no memory
management) will only be able to 'see' the bottom 56KB.
> Is it ok for the installed RA mto overlap the 8kW at the high memory
> area?
Yeah, what the CPU sees as the I/O page (at 0160000-0177776 in its address
space) is actually at 0760000-0777776 on the QBUS (on a Q18 QBUS); the CPU
automagically translates the 0160000-0177776 addresses up. On a PDP-11
with memory management, the MMU has to be set up to do that. E.g. in V6,
in:
https://minnie.tuhs.org//cgi-bin/utree.pl?file=V6/usr/sys/conf/m40.s
there is the following code:
/ initialize io segment
mov $IO,(r0)+
mov $77406,(r1)+ / rw 4k
to set the I/O page in kernel address space to point to the I/O page on the
bus.
Noel
next reply other threads:[~2020-09-30 17:59 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-30 17:58 Noel Chiappa [this message]
-- strict thread matches above, loose matches on Subject: below --
2021-02-03 1:25 Noel Chiappa
2020-10-18 21:36 Norman Wilson
2020-10-12 22:43 Noel Chiappa
2020-10-12 19:27 Noel Chiappa
2020-10-10 23:29 Noel Chiappa
2020-10-11 2:30 ` Jay Logue
2020-10-11 23:24 ` Paul Riley
2020-10-12 0:53 ` Dave Horsfall
2020-10-12 1:56 ` Warner Losh
2020-10-12 2:09 ` Andrew Warkentin
2020-10-12 16:57 ` Arthur Krewat
2020-10-18 20:42 ` Michael Huff
2020-10-08 23:49 Noel Chiappa
2020-10-08 16:06 Noel Chiappa
2020-10-06 23:08 Noel Chiappa
2020-10-07 5:24 ` Jay Logue
2020-10-06 20:34 Noel Chiappa
2020-10-06 19:34 Noel Chiappa
2020-10-06 19:04 Noel Chiappa
2020-10-06 14:46 Noel Chiappa
2020-10-06 16:22 ` jay-tuhs9915
2020-10-02 0:39 Noel Chiappa
2020-10-01 12:51 Noel Chiappa
2020-10-02 0:23 ` Paul Riley
2020-09-30 23:16 Noel Chiappa
2020-09-30 18:51 Noel Chiappa
2020-09-28 23:21 Noel Chiappa
2020-09-30 1:50 ` Paul Riley
2020-09-27 21:07 Noel Chiappa
2020-09-27 21:12 ` Warner Losh
2020-09-28 0:22 ` Pete Turnbull
2020-09-27 20:50 Noel Chiappa
2020-09-29 13:20 ` Paul Riley
2020-09-25 22:08 Noel Chiappa
2020-09-26 14:52 ` John Foust
2020-09-28 0:03 ` Paul Riley
2020-09-28 0:06 ` Paul Riley
2020-09-24 18:56 Noel Chiappa
2020-09-24 13:04 Noel Chiappa
2020-09-24 18:24 ` John Cowan
2020-09-24 11:02 Paul Ruizendaal
2021-02-03 0:12 ` Greg A. Woods
2020-09-24 1:28 Noel Chiappa
2020-09-23 23:14 Noel Chiappa
2020-09-24 1:09 ` John Foust
2020-09-22 21:51 John Foust
2020-09-22 21:36 Noel Chiappa
2020-09-22 21:46 ` Warner Losh
2020-09-22 21:49 ` John Foust
2020-09-22 15:59 Noel Chiappa
2021-02-03 0:07 ` Greg A. Woods
2020-09-22 0:47 Noel Chiappa
2020-09-21 19:37 Noel Chiappa
2020-09-21 23:16 ` devin davison
2020-09-21 18:13 Noel Chiappa
2020-09-21 17:59 Noel Chiappa
2020-09-21 18:18 ` Arthur Krewat
2020-09-20 13:12 Noel Chiappa
2020-09-19 15:28 Noel Chiappa
2020-09-21 10:26 ` Paul Riley
2021-01-24 16:07 ` Tom Ivar Helbekkmo via TUHS
2021-01-25 4:58 ` Gregg Levine
2021-01-25 8:21 ` Tom Ivar Helbekkmo via TUHS
[not found] <CAD05_j1bc6DDRtfPkd4QVeWXjwSp73bty46D=2ATozUbHThBWw@mail.gmail.com>
2020-09-19 3:22 ` Paul Riley
2020-09-19 14:20 ` Heinz Lycklama
2020-09-21 13:54 ` Paul Riley
2020-09-21 15:30 ` Heinz Lycklama
2020-09-21 23:27 ` Henry Bent
[not found] ` <4C35E6D2-8ABD-4DC2-BB2F-F15FA5BF30DD@icloud.com>
2020-09-22 0:22 ` Henry Bent
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200930175817.4575B18C0B2@mercury.lcs.mit.edu \
--to=jnc@mercury.lcs.mit.edu \
--cc=tuhs@minnie.tuhs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).