why PDP-12 after PDP-11
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Peter Peterson
Jun 17, 2019, 12:37:28 PM6/17/19
to PDP-12 Restoration Project
Hi all,
I just spent a few minutes looking for this answer, but couldn't find it. Why did the PDP-12 come out before the PDP-11? Was the -11 meant to come out sooner but missed a deadline?
Thanks,
Peter
--
Department of Computer Science
University of Minnesota Duluth
Peter A. H. Peterson, Ph.D.
Assistant ProfessorDepartment of Computer Science
Nick Moffitt
Jun 17, 2019, 1:24:26 PM6/17/19
to PDP-12 Restoration Project
Or was it just that the -11 project started earlier but took longer to complete? It would seem that the -12 was making use of two pre-existing architectures, and could probably kit-bash them quicker than building a new 16-bit machine from the ground up.
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CLASystems
Jun 17, 2019, 1:53:13 PM6/17/19
to Peter Peterson, PDP-12 Restoration Project
On Mon, Jun 17, 2019 at 12:37 PM Peter Peterson <pa...@d.umn.edu> wrote:
Hi all,I just spent a few minutes looking for this answer, but couldn't find it. Why did the PDP-12 come out before the PDP-11? Was the -11 meant to come out sooner but missed a deadline?
The PDP-12 was to be called the LINC-8/I which makes more sense. at least one module in the machine has that name in the artwork.
The numbers past that are somewhat of a mystery, likely "reserved" names demanded by dueling salesmen.
It is believed that the (fortunately) never produced model of a PDP-8 with drum-type memory (in the general sense) was to be known as the PDP-10, this is likely because at the time it was the next number up and in an era of no internal marketing strife (relatively). This machine "survives" in the form of the DF32 disk which is actually exactly 32K, the largest allowed in a DEC 12-bit machine (until the KT8A) and can even be had with parity, which would otherwise be rare in a disk.
The -11 nomenclature was probably a placeholder for what eventually became the DG Nova when that project was canned over a weekend thanks to the ego of C. Gordon Bell who was swayed by two newbie hires who brought him the pathetic design of the PDP-11 described in his notation from Bell's recent book. As a result, he scuttled the well-planned 16-bit machine project, and Edson De Castro, designer of the PDP-8 and PDP-8/I and PDP-8/L took all about 200 employees with him and formed Data General. Since it was all in their collective heads and no documents, DEC had no ability to sue, etc.
The -11 as proffered up suffers from sloppy design elements prompting a paper to be written called something like The PDP-11: A case study in how to NOT design condition-code architecture.
There are gross sloppinesses that a careful review would have eliminated, but Bell pulled strings and it was never vetted. There are problems such as the precise condition code results of the increment and decrement instructions differ respectively from adding one and subtracting 1 (and you then have to consider the inverse cases such as subtracting -1 and adding -1, etc.
In any case, marketeers decided the -12 needed a new number thus shot down LINC-8/I. The PDP-10 became an appropriate number for a great machine, but largely based on the -6, sorta like the 7 begets the 9 and the -5 begets the -8. It is arguable the PDP-15 should have been 9/I but there was a 9/L meaning lowered cost, thus that would be confusing. -13 is of course just bad luck, and -14 is just a design principal and a bunch of its own K modules blacK.
And there are of course theories of why no 2 and 3, claimed as because the PDP-1 was THE PDP and the manual is 1 then 2 then 3.
The numbers past that are somewhat of a mystery, likely "reserved" names demanded by dueling salesmen.
It is believed that the (fortunately) never produced model of a PDP-8 with drum-type memory (in the general sense) was to be known as the PDP-10, this is likely because at the time it was the next number up and in an era of no internal marketing strife (relatively). This machine "survives" in the form of the DF32 disk which is actually exactly 32K, the largest allowed in a DEC 12-bit machine (until the KT8A) and can even be had with parity, which would otherwise be rare in a disk.
The -11 nomenclature was probably a placeholder for what eventually became the DG Nova when that project was canned over a weekend thanks to the ego of C. Gordon Bell who was swayed by two newbie hires who brought him the pathetic design of the PDP-11 described in his notation from Bell's recent book. As a result, he scuttled the well-planned 16-bit machine project, and Edson De Castro, designer of the PDP-8 and PDP-8/I and PDP-8/L took all about 200 employees with him and formed Data General. Since it was all in their collective heads and no documents, DEC had no ability to sue, etc.
The -11 as proffered up suffers from sloppy design elements prompting a paper to be written called something like The PDP-11: A case study in how to NOT design condition-code architecture.
There are gross sloppinesses that a careful review would have eliminated, but Bell pulled strings and it was never vetted. There are problems such as the precise condition code results of the increment and decrement instructions differ respectively from adding one and subtracting 1 (and you then have to consider the inverse cases such as subtracting -1 and adding -1, etc.
In any case, marketeers decided the -12 needed a new number thus shot down LINC-8/I. The PDP-10 became an appropriate number for a great machine, but largely based on the -6, sorta like the 7 begets the 9 and the -5 begets the -8. It is arguable the PDP-15 should have been 9/I but there was a 9/L meaning lowered cost, thus that would be confusing. -13 is of course just bad luck, and -14 is just a design principal and a bunch of its own K modules blacK.
And there are of course theories of why no 2 and 3, claimed as because the PDP-1 was THE PDP and the manual is 1 then 2 then 3.
cjl
Thanks,Peter--University of Minnesota DuluthPeter A. H. Peterson, Ph.D.Assistant Professor
Department of Computer Science
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CLASystems
Jun 17, 2019, 2:17:34 PM6/17/19
to Nick Moffitt, PDP-12 Restoration Project
On Mon, Jun 17, 2019, 1:24 PM Nick Moffitt <ni...@zork.net> wrote:
Or was it just that the -11 project started earlier but took longer to complete? It would seem that the -12 was making use of two pre-existing architectures, and could probably kit-bash them quicker than building a new 16-bit machine from the ground up.
Not really; apparently few are aware of the Nova debacle. If anything. the release of the horrible design of the 11-10 (the opinion of even -11 lovers) was absurdlly rushed. That said, the 16-bit Nova was very carefully designed and started much earlier. Even the number was stollen.
CLASystems
Jun 17, 2019, 2:20:39 PM6/17/19
to Nick Moffitt, PDP-12 Restoration Project
And as I posted earlier, it was to be the LINC-8/I.
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