[fpc-devel] 64 Bit / 32 Bit
almindor at gmail.com
Tue Oct 2 10:40:26 CEST 2007
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> Oops ?!?! I supposed that using the much greater count of registers
> in 64 bit mode could speed up any kind of software. I suppose that
> the experts _are _working on that, though.
Registers are only so useful. I have a very nice example program which
is roughly 2x slower on 64bit version (on same machine) than 32bit
version. It was a school project which did some tree search/generation
(AI stuff) and had to use quite a lot of memory. The explanation of
this slowdown given to me was simple.
In 64bits, the cache is same as in 32bits (same machine remember?),
but the amount of memory not (pointers, alignment I guess? etc.)
I don't know the internals to know which things cause bigger cache
hugging on 64bits, I'd guess at least pointers do, but perhaps
everything is "native padded" for speed?
> Thanks for your answers !
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