[rescue] Re: [geeks] THIS. MAKES. ME. SICK.

rescue at sunhelp.org rescue at sunhelp.org
Wed Jun 13 19:40:46 CDT 2001

mcguire at neurotica.com writes:

>On June 13, dave at cca.org wrote:
>> That wouldn't gain you anything. The performance difference between
>> a workstation and a super these days is almost entirely due to the
>> memory bandwidth & IO.

>  *bzzzzt*  Thank you for playing.

Ah, bullshit. :-)

>  You've forgotten about the performance of the processor, and the
>number of processors.  A Cray T932/32 can deliver a sustained 64GFLOPS
>of big-testicle 64-bit floating-point power.  You point me to a
>workstation that can do that, and I'll eat cat food in order to buy

They can't because they're crippled by the memory bandwidth. The 
latest RISC chips have peak theoretical FLOPS in the same ballpark
as Cray. They don't get *anywhere* *near* that performance,
because they're crippled by the rest of the machine, primarily the
memory bandwidth.

The number of processors has nothing to do with vector versus
plain-old-RISC. What I'm saying is that the outrageous performance
of the Cray vector machines, compared to todays high-end RISC
machines, is primarily, almost entirely, the rest of the box,
not the fact that it has vector instructions.

>> What surprises me is that we haven't seen a standard RISC chip thrown
>> in a box with a Cray-class memory system. (Well, I suppose that's what
>> the J90 is, actually...)

>  ...and, well, vector execution units.  And multiple processors.  And a
>crossbar switch for memory access.  And multiple I/O processors.  And
>the fact that the Cray PVP architecture isn't very RISC-like.

Woo - memory and IO. I said that, didn't I? Take a Cray, and replace the
CPUs with standard RISC chips. I don't think there would be much difference.

You might argue that it would be impossible to take advantage of that
much bandwidth without scatter/gather hardware. I'll give that one
point to the vector CPUs.

I consider Crays to be entirely RISC. RISC = Really Invented by Seymour
Cray, eh?

After all the hype and dust from the late 80s disappeared, what 
features defined "RISC"? Load/store and fixed-length instructions.
That's really all. Seymour invented that back in the mid 60s.

-- david fischer -- dave at cca.org -- www.cca.org -- Cthulhu told me to. --

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