[rescue] ooh, pretty

[Francisco Javier Mesa-Martinez]

> A researcher I was acquanted with used to run large compute jobs taking
> several weeks to finish. She switched to a dual R10K Octane and 1 run
> later switched back to a Power Indigo2 (with a 75Mhz R8K).
>
> Don't fall into the trap of assuming Mhz=speed (Dave obviously knows
> this) ... a quote from a supercomputing centre looking at the R8000
> said that it was half the clock speed of the R4400 but 4 times the
> speed (probably just looking at fp perf).

Actually the R8K (nee the TFP) was a b**ch to code! Yeah, I had to run
some of our code in some early challenge, and it was just a plain pain in
the neck. A lot of our code had to be tuned by hand, which we were used to
do to begin with, but I had the "performance tuning guide for the R8K"
open in my lap on a daily basis when using those machines. You had to put
the instructions just right to keep the superscalar FP unit happy.
Conditionals and such were also a pain to schedule, plus the integer unit
was pretty weak.

>From experience any code ran faster on the R10K machines, even the stuff
developed especifically for the R8K. In fact the only reason why my
previous group stayed with sgi for so long, was that we had invested a lot
of hours on r8k code. So I find it hard to believe that anyone would find
an I2 R8K faster than a dual R10K octane. As far as I know the fpu units
are pretty much identical. the R10K is a more balanced design, plus it has
the facilities to do true superscalar processign, unlike the half assed
effort by the r8K. For most of our fp code the R10K was about double the
performance than our 90Mhz R8K's, so it seems that mghz per mghz the two
chips were comparable. thisi is from our experience I do not have spec
numbers though...


I also used to have a teal powerI2, and I do not recommend it. It is not a
good chip for the desktop, since the int unit is slower than a 200Mhz
R4400. I remember the early impacts had R8K's though, I have some
brochures from the introduction of the impact, and they mention 2 R4x00
models and a R8K model. But I have only seen R10K impacts....