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Subject: Re: The big waste

Author: Omid David Tabibi

Date: 12:17:29 09/21/03

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On September 21, 2003 at 08:45:23, Gerd Isenberg wrote:

>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].

Wouldn't a heavy use of unsigned type variables (whenever possible) alleviate
this problem?


>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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