From: bqt@update.uu.se (Johnny Billquist)
Subject: [TUHS] PDP-11/70 SPL
Date: Mon, 28 Mar 2016 18:37:01 +0200 [thread overview]
Message-ID: <56F95DAD.4050105@update.uu.se> (raw)
In-Reply-To: <0BAE4C73-C72B-453E-BEBD-EA34CEEA9853@uwlax.edu>
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 1674 bytes --]
Thanks for some additional information.
On 2016-03-28 18:16, Milo Velimirović wrote:
>
>> On Mar 28, 2016, at 9:44 AM, Johnny Billquist <bqt at update.uu.se> wrote:
>>
>> On 2016-03-28 16:18, Noel Chiappa wrote:
>>> > From: Dave Horsfall <dave at horsfall.org>
>>>
>
> [ Wait & RK discussion snipped.]
>
>>
>>
>>> > I know that Kevin Dawson (I think) tried it on my /40 as well
>>>
>>> The 11/40 does not have the SPL instruction; see the '75-'76 PDP-11 Processor
>>> Handbook, pg. 4-5. (Again, sorry, just want to be accurate.)
>>
>> This is also a pretty important point. But one which also begs the question how the splxxx() functions in Unix worked back then. Or did Unix not use this pattern and these functions back when the 11/40 was relevant?
>
> These functions existed in V6 and can be found in the file, m40.s, that was assembled with the rest of the kernel to generate a unix that would run on a /40 class machine.
Aha. Great. Thanks. Yes, BIS and BIC on the PSW obviously works, but
this would definitely not block interrupts for the next instruction. So
at least in that case, a WAIT could result in the kernel sitting around
waiting for the next interrupt. I don't really think DEC intend WAIT to
be used in the way Unix uses it, and it don't really have the properties
that would be ideas for Unix. Also somewhat indicated by the fact that
DEC did not use WAIT this way themselves.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
next prev parent reply other threads:[~2016-03-28 16:37 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-28 14:18 Noel Chiappa
2016-03-28 14:44 ` Johnny Billquist
[not found] ` <0BAE4C73-C72B-453E-BEBD-EA34CEEA9853@uwlax.edu>
2016-03-28 16:37 ` Johnny Billquist [this message]
2016-03-28 16:52 ` Milo Velimirović
-- strict thread matches above, loose matches on Subject: below --
2016-03-28 13:43 Noel Chiappa
[not found] <mailman.171.1459115387.15972.tuhs@minnie.tuhs.org>
2016-03-27 23:07 ` Johnny Billquist
2016-03-28 13:37 ` Dave Horsfall
2016-03-28 15:18 ` John Cowan
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=56F95DAD.4050105@update.uu.se \
--to=bqt@update.uu.se \
/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).