Author: Gerd Isenberg
Date: 05:45:23 09/21/03
Interesting articles in german's magazin c't about 64-bit processors:
"The big waste" - even with 32-bit processors, more than 50% of all cache- and
memory resources are wasted for the sign-bit [1]. About 75% of all moved bits
are zeros (32-bit), which will increase with 64-bit processors.
A currently not available sign-compression may safe 20% energy.
Bit-size of some datatypes of 64-bit C(C#) compilers (32-bit / 64-bit):
MSC MS C# gcc
int 32/32 32/32 32/32
long 32/32 64/64 32/64
__int64 64/64 - -
ULONG_PTR 32/64 - -
long long - - 64/64
An interesting side note on Opteron's x87-FPU/MMX-3DNow. Suse Linux will support
x87-FPU/MMX-3DNow, even per default float and double arithmetic is done by
SSE/SSE2.
And probably the "last word" for ms political/educational decision, not to
save/restore x87-FPU/MMX-registers during context switch in 64-bit mode is not
finally spoken...
Hopefully. MMX and SSE2 does complement for 64-bit and 2*64-bit SIMD integer
arithmetic.
Cheers,
Gerd
[1] Zhang, Gupta
Enabling Partial Cache Line Prefetching Through Data Compression
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