From: bqt@update.uu.se (Johnny Billquist)
Subject: [TUHS] pdp11 UNIX memory allocation.
Date: Wed, 07 Jan 2015 00:34:06 +0100 [thread overview]
Message-ID: <54AC70EE.4060301@update.uu.se> (raw)
In-Reply-To: <mailman.151.1420584979.3354.tuhs@minnie.tuhs.org>
On 2015-01-06 23:56, Clem Cole<clemc at ccc.com> wrote:
>
> On Tue, Jan 6, 2015 at 5:45 PM, Noel Chiappa<jnc at mercury.lcs.mit.edu>
> wrote:
>
>> >I have no idea why DEC didn't put it in the 60 - probably helped kill that
>> >otherwise intersting machine, with its UCS, early...
>> >
> ?"Halt and confuse ucode" had a lot to do with it IMO.
>
> FYI: The 60 set the record of going from production to "traditional
> products" faster than? anything else in DEC's history. As I understand
> it, the 11/60 was expected to a business system and run RSTS. Why the WCS
> was put in, I never understood, other than I expect the price of static RAM
> had finally dropped and DEC was buying it in huge quantities for the
> Vaxen. The argument was that they could update the ucode cheaply in the
> field (which to my knowledge the never did). But I asked that question
> many years ago to one of the HW manager, who explained to me that it was
> felt separate I/D was not needed for the targeted market and would have
> somehow increased cost. I don't understand why it would have cost any
> more but I guess it was late.
No, field upgrade of microcode can not have been it. The WCS for the
11/60 was an option. Very few machines actually had it. It was for
writing your own extra microcode as addition to the architecture.
The basic microcode for the machine was in ROM, just like on all the
other PDP-11s. And DEC sold a compiler and other programs required to
develop microcode for the 11/60. Not that I know of anyone who had them.
I've "owned" four PDP-11/60 systems in my life. I still have a set of
boards for the 11/60 CPU, but nothing else left around.
The 11/60 was, by the way, not the only PDP-11 with WCS. The 11/03 (if I
remember right) also had such an option. Obviously the microcode was not
compatible between the two machines, so you couldn't move it over from
one to the other.
Also, reportedly, someone at DEC implemented a PDP-8 on the 11/60,
making it the fastest PDP-8 ever manufactured. I probably have some
notes about it somewhere, but I'd have to do some serious searching if I
were to dig that up.
But yes, the 11/60 went from product to "traditional" extremely fast.
Split I/D space was one omission from the machine, but even more serious
was the decision to only do 18-bit addressing on it. That killed it very
fast.
Someone else mentioned the MFPI/MFPD instructions as a way of getting
around the I/D restrictions. As far as I know (can tell), they are
possible to use to read/write instruction space on a machine. I would
assume that any OS would set both current and previous mode to user when
executing in user space.
The documentation certainly claims they will work. I didn't think of
those previously, but they would allow you to read/write to instruction
space even when you have split I/D space enabled.
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 parent reply other threads:[~2015-01-06 23:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.151.1420584979.3354.tuhs@minnie.tuhs.org>
2015-01-06 23:34 ` Johnny Billquist [this message]
2015-01-06 23:52 ` scj
2015-01-07 16:14 ` Clem Cole
2015-01-07 17:27 ` Dave Horsfall
2015-01-07 2:18 Noel Chiappa
2015-01-07 16:17 ` Clem Cole
-- strict thread matches above, loose matches on Subject: below --
2015-01-06 22:45 Noel Chiappa
2015-01-06 22:55 ` Clem Cole
[not found] <mailman.149.1420581544.3354.tuhs@minnie.tuhs.org>
2015-01-06 22:20 ` Johnny Billquist
2015-01-06 22:36 ` Ronald Natalie
2015-01-06 23:14 ` Johnny Billquist
2015-01-07 2:39 ` John Cowan
2015-01-07 2:59 ` Johnny Billquist
[not found] <mailman.147.1420574271.3354.tuhs@minnie.tuhs.org>
2015-01-06 20:20 ` Johnny Billquist
2015-01-06 20:33 ` random832
2015-01-06 21:57 ` Ronald Natalie
2015-01-06 22:00 ` Clem Cole
2015-01-06 22:04 ` Ronald Natalie
2015-01-07 1:46 ` Dave Horsfall
2015-01-07 2:00 ` Ronald Natalie
2015-01-07 6:29 ` Dave Horsfall
2015-01-07 6:39 ` Warren Toomey
2015-01-07 10:06 ` Brantley Coile
2015-01-07 13:29 ` Jacob Ritorto
[not found] ` <CAC20D2PP1hGyYsep1yNtj9KO55a-V02+QHS+S7bX-4joJy222g@mail.gmail.com>
[not found] ` <1420583703.863814.210431037.61D6C6EC@webmail.messagingengine.com>
2015-01-06 22:36 ` random832
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