15 Nov
2017
15 Nov
'17
5:25 a.m.
On Nov 14, 2017, at 10:58 PM, Jon Elson via cctalk
<cctalk at classiccmp.org> wrote:
On 11/14/2017 11:20 AM, Chuck Guzis via cctalk wrote:
I can't remember how many transistors a CDC 6600 has. A lot more than that, I'm
pretty sure.
On "quirky arcane instruction sets" -- some yes, some no. The CDC 6000 series
can make a pretty good argument for being the first RISC machine. Its instructions are
certainly quite nicely constructed and the decoding involved is pretty compact. While I
don't think the term "orthogonal" had been applied yet to instruction set
design -- I first saw that used for the VAX -- it fits the 6000 too.
Another example of an instruction set design that's pretty orthogonal is the
Electrologica, especially in the X1 (from 1958). It's a one address machine, not a
register machine like the 6000 or traditional RISC, but in other ways it looks a lot like
RISC. Wide instructions with fixed fields allocated for fixed purposes (like register
numbers, operation numbers, conditional execution modifiers, etc.).
The 360 was certainly significant in delivering many of these things in a very successful
commercial package. And I can believe it being revolutionary for IBM -- but not quite so
much for the industry as a whole.
paul
It's always struck me how revolutionary (for
IBM) the change in
architecture from the 700x to the S/360 was. The 709x will probably
strike the average reader of today as being arcane, what with
sign-magnitude representation, subtractive index registers and so on.
The 7080, probably even more so. But then, most of IBM's hardware
before S/360 had its quirky side; the only exception I can think of,
offhand, would be the 1130, which was introduced at about the same time
as the S/360.
Pretty much all computers of that early-60's vintage, where a
maze of logic was used to decode instructions, and everything was done with discrete
transistors and diodes, had quirky arcane instruction sets. Some of this was due to the
prevailing thought on instruction sets, but part of it was done to save a few transistors
here and there, and to heck with the side effects. Most of these computers had very few
registers, or put the "registers" in fixed core locations, due to the cost of a
flip-flop. The 709x series was certainly like that. Hard to BELIEVE, with 55,000
transistors!