Java 6-what we really got?

[Riven]

Only the Core2 CPUs are actually doing 4 at the same time.

The others (AMD, Intel P4) are doing 2 pairs internally...

Next generation AMD will also do 4 in parallel.

[darkprophet]

really? How did our little SIMD instruction library give us a 4.2x speed increase when doing a SQRT on a P4 ?

[Riven]

I realized that while it typed it, but the CPU specs say it does 2 pairs...

MUL/SUB/ADD/DIV were barely faster than factor 2, so appearantly SQRT is not only done in SIMD, but also calculated twice as fast...?

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[darkprophet]

that explains why everything other than SQRT was giving a 2.4x speed increase then! Yay, we finally have a proper explanation....

although why is SQRT so much faster under SSE2 then?

[Linuxhippy]

Only SIMD is for CPU's and SSE2/3 only support 4 data streams at 1 point while modern GPUs support 32 (the G80 supports 64 doesn't it ?

Well but the G80 is no CPU therefor ... its quite different.
I think the whole reorder, pipeline, SIMD stuff in todays processors is a big waste.
In how many percent all of the 4 integer units of a Core2 can be fad with a single instruction stream - I guess not in even 1% of total execution time all 4 units work - wasted silicon.

I know there are things that are hard to do in paralell programming, but I think a design with e.g. one Core2-Core and one Sun-T1 design side-by-side would be optimal.

lg Clemens