Nagered hard drive;'(..
in [Computer]
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From: Bob Eager on 25 Jun 2010 18:38 On Fri, 25 Jun 2010 22:14:00 +0100, Tim Streater wrote: >> > Could you define what's meant by "multiprogramming support" in this >> > context? >> >> Two operating modes - user and executive. Or did I get it wrong and the >> 4120 had that too? Enter user mode with the EXIT instruction, and >> system call back with the EXEN instruction... > > Yeah, OK, that's pretty common. I guess I never heard it called that > before. But the I never used any ICL kit. There's obvioously more, if it is to be useful, but that's a good start. We had a Honeywell DDP-516 that had a two-mode operation, but it was useless as (for example) there was no way of telling the previous state when an interrupt had occurred, so you couldn't restore state. Quite a lot of other holes too. I rewired the CPU to fix the variouls issues. -- Use the BIG mirror service in the UK: http://www.mirrorservice.org *lightning protection* - a w_tom conductor
From: Bob Eager on 25 Jun 2010 20:00 On Sat, 26 Jun 2010 00:14:37 +0100, Tim Streater wrote: > In article <88kpeiFiv6U5(a)mid.individual.net>, > Bob Eager <rde42(a)spamcop.net> wrote: > >> On Fri, 25 Jun 2010 22:14:00 +0100, Tim Streater wrote: >> >> >> > Could you define what's meant by "multiprogramming support" in >> >> > this context? >> >> >> >> Two operating modes - user and executive. Or did I get it wrong and >> >> the 4120 had that too? Enter user mode with the EXIT instruction, >> >> and system call back with the EXEN instruction... >> > >> > Yeah, OK, that's pretty common. I guess I never heard it called that >> > before. But then I never used any ICL kit. >> >> There's obvioously more, if it is to be useful, but that's a good >> start. >> >> We had a Honeywell DDP-516 that had a two-mode operation, but it was >> useless as (for example) there was no way of telling the previous state >> when an interrupt had occurred, so you couldn't restore state. Quite a >> lot of other holes too. I rewired the CPU to fix the variouls issues. > > Blimey wot was the point of that then (designing it that way, I mean). > > You prolly want to be able to designate memory as no-access, read-only, > read/write, and execute-only, too (as well as mapping it). > > I remember going to a presentation on the then-new 68000 in 1979 where > folks were asking about such features (and also what you mentioned), but > the Motorola guy said that they figured it would take too much space on > the chip. Turns out that later, when they looked into it, it didn't add > much extra at all. It was only a little 16 bit machine, predating the PDP-11. Thousands of them were node processors on ARPANet. No idea why they did it like that...but history is littered with half baked solutions. I would guess cost. The 386 didn't correctly trap certain instructions, it just made them no-ops...which means hardware virtualisation wasn't possible. That fed through up to Pentiums quite recently. Now there's yet another operating mode to select to make it work as it should have done. (this rather ignores the fact that partial software virtualisation can actually be more efficient anyway!) -- Use the BIG mirror service in the UK: http://www.mirrorservice.org *lightning protection* - a w_tom conductor
From: Roland Perry on 26 Jun 2010 03:09 In message <2_mdnVnocdLrvrjRnZ2dnUVZ8r0AAAAA(a)brightview.co.uk>, at 22:44:26 on Fri, 25 Jun 2010, Jon Green <jonsg(a)deadspam.com> remarked: >> No, the one I have is acoustic. > >Oh, the springy thingy? Inside there's a couple of large loops, technically it's a coil, but that's a confusing way to describe it. -- Roland Perry
From: dennis on 26 Jun 2010 03:32 "Tim Streater" <timstreater(a)waitrose.com> wrote in message news:timstreater-341A48.00143726062010(a)news.individual.net... > In article <88kpeiFiv6U5(a)mid.individual.net>, > Bob Eager <rde42(a)spamcop.net> wrote: > >> On Fri, 25 Jun 2010 22:14:00 +0100, Tim Streater wrote: >> >> >> > Could you define what's meant by "multiprogramming support" in this >> >> > context? >> >> >> >> Two operating modes - user and executive. Or did I get it wrong and >> >> the >> >> 4120 had that too? Enter user mode with the EXIT instruction, and >> >> system call back with the EXEN instruction... >> > >> > Yeah, OK, that's pretty common. I guess I never heard it called that >> > before. But then I never used any ICL kit. >> >> There's obvioously more, if it is to be useful, but that's a good start. >> >> We had a Honeywell DDP-516 that had a two-mode operation, but it was >> useless as (for example) there was no way of telling the previous state >> when an interrupt had occurred, so you couldn't restore state. Quite a >> lot of other holes too. I rewired the CPU to fix the variouls issues. > > Blimey wot was the point of that then (designing it that way, I mean). IME you add some "useful" hardware feature and the programmers can't grasp how to use so it just sits there untested and never gets fixed if its broken. I've been there.. I designed part of a redundant processor system where each CPU could monitor the interrupts and the responses on the other CPUs. So if an interrupt occurred and the CPU running the lowest priority process didn't respond another would kick off a fault interrupt. The hardware worked great but the idea was too hard for the "software" and it got removed during testing. Intel later infringed the patent I had on interrupting the lowest priority "CPU" but because we didn't use the idea someone decided the to let the patent lapse. > > You prolly want to be able to designate memory as no-access, read-only, > read/write, and execute-only, too (as well as mapping it). > > I remember going to a presentation on the then-new 68000 in 1979 where > folks were asking about such features (and also what you mentioned), but > the Motorola guy said that they figured it would take too much space on > the chip. Turns out that later, when they looked into it, it didn't add > much extra at all. I expect the machine predates the 68000. Motorola completely mucked up the MMU they designed. They went through several versions before they got one that worked properly and put it in the 68030. In the meantime Intel had produced the 386 which had a working paged MMU in it and that was what later became the normal way of doing paged memory on Unix and the likes. Prior to that nearly every Unix machine had different paging mechanisms.
From: Rupert Moss-Eccardt on 26 Jun 2010 07:09
Bob Eager wrote: > On Fri, 25 Jun 2010 15:25:43 +0000, Huge wrote: > >> On 2010-06-25, Roland Perry<roland(a)perry.co.uk> wrote: >>> In message<88jcpkFs8lU7(a)mid.individual.net>, at 09:56:04 on Fri, 25 >>> Jun 2010, Huge<Huge(a)nowhere.much.invalid> remarked: >>>>> In mid 70's I worked on ICL drives, including something they called a >>>>> "drum", which was a single-platter mounted vertically. >>>> >>>> You sure it was a "platter"? Only, when I worked for ITT in around >>>> 1975/6 (on what became the Unimat 4080 telephone switch), the message >>>> switches that we shared our computer room with definitely had drums >>>> that were drum shaped. >>> >>> Absolutely sure. >> >> It appears that ICLs weird storage topology terminology was unknown to >> me. Not surprising. I was a MUMPS programmer roped in to help rewrite >> ATV's payroll system in RPG2 (spit) and port it from a 1904S (I think) >> to a 2903. That was my only exposure to ICL kit - I left shortly >> afterwards to return to my beloved PDP11s and trying to weigh flying >> crisps. > > I think that's right, though....ICL did keep a lot of old terminology > around. As well as inventing new stuff - like the CPU becoming an OCP > (Order Code Processor) Ah, but the CPU was the whole box. The OCP was the 'mill'. |