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From: Rob Warnock on 30 Mar 2010 21:41
MitchAlsup <MitchAlsup(a)aol.com> wrote:
+---------------
| The most memorable hardware structure is the vector indirect
| addressing mode.
+---------------

I was always rather fond of the PDP-10's multi-level indirect addressing
which allowed additional indexing with a different accumulator at each
level of indirection, and how that permitted multi-dimension array indexing
to be done in a *single* instruction, albeit requiring auxiliary Iliffe
vectors for the arrays [as was done in ALGOL-10]. Quoting myself:

Newsgroups: alt.folklore.computers
Date: Sun, 30 Aug 2009 06:03:04 -0500
From: rpw3(a)rpw3.org (Rob Warnock)
Subject: Re: PDP-10 Assembly Language Questions
Message-ID: <HrWdnRhVz531wQfXnZ2dnUVZ_v6dnZ2d(a)speakeasy.net>
...
For, say, a three-dimensional array, if A, B, & C were already
in the proper registers, then "FOO[A,B,C] := FOO[A,B,C] + 1"
could be done in *one* instruction!! (No joke!)
What, you don't believe me? ;-} Here's the code:

MOVE T1,A ; Load up the array indices
MOVE T2,B
MOVE T3,C
AOS @FOO(T1) ; Increment FOO[A,B,C] (and don't skip).

[Assumes the first level of Iliffe vectors has the indirect-addressing
bit on and "T2" in the index field, and the second level of Iliffe vectors
has the indirect-addressing bit *off* and "T3" in the index field.]


-Rob

-----
Rob Warnock <rpw3(a)rpw3.org>
627 26th Avenue <URL:http://rpw3.org/>
San Mateo, CA 94403 (650)572-2607

From: MitchAlsup on 1 Apr 2010 18:22
On Apr 1, 1:07 pm, glen herrmannsfeldt <g...(a)ugcs.caltech.edu> wrote:
> The explanation I have seen for the CDB, common data bus, was
> that results come out broadcast to all possible destinations.

Do you realize that the length of this bus and the number of
destination nodes was one of the reasons the IBM machine topped out at
60ns while the CDC machines topped out at 27.5ns and could deliver 4
result (and one load) per cycle (as catch-up bandwidth).

Mitch

From: Robert Myers on 1 Apr 2010 22:20
On Apr 1, 10:05 pm, "Andy \"Krazy\" Glew" <ag-n...(a)patten-glew.net>
wrote:

> Myself, I thought it was obvious.

There's your problem right there, Andy. Everyone else will say:

1. It's already been done (heard way too many times in this forum).

2. It was obvious (emphasis on the past tense).

People answering either (1) or (2) assume that everything that can be
thought of is already in textbooks. That's how they got to where they
are.

Robert.

From: MitchAlsup on 1 Apr 2010 22:48
On Apr 1, 9:05 pm, "Andy \"Krazy\" Glew" <ag-n...(a)patten-glew.net>
wrote:
> I also talked to Mitch about it at around that time, although he was preoccupied with spreadsheets for the

Any chance you could complete this sentance?

Perhaps from {88100, 88110, 88120, crazy, insane, Asilomar
participants, Hot Chips participants, all of the preceeding?}

Mitch
From: KJ on 2 Apr 2010 00:28
On Apr 1, 10:20 pm, Robert Myers <rbmyers...(a)gmail.com> wrote:
> On Apr 1, 10:05 pm, "Andy \"Krazy\" Glew" <ag-n...(a)patten-glew.net>
> wrote:
>
> > Myself, I thought it was obvious.
>
> There's your problem right there, Andy.  Everyone else will say:
>
> 1. It's already been done (heard way too many times in this forum).
>
> 2. It was obvious (emphasis on the past tense).
>
> People answering either (1) or (2) assume that everything that can be
> thought of is already in textbooks.  That's how they got to where they
> are.
>

Textbooks? Didn't you get the memo? Everything that can be thought
of is on Google...or should I say Topeka ;)

KJ
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