Subject: Re: Incredible!
From: Timothy A. Seufert (tas@mindspring.com)
Date: Wed Sep 12 2001 - 17:07:45 MDT
At 5:16 PM -0400 9/12/01, Sean O. Denney wrote:
>Yes, but Altivec's 128-bit registers and shorter pipelines make the
>processor perform more operations per clock cycle than the P4's 32-bit
>registers and longer pipelines. Even if the program you are using
>doesn't use Altivec, the PPC G4's FPU registers are 64-bit, double
>that of the P4.
Nonsense. The x87 FPU (P4 implementation included) has 80-bit FP
registers. It supports IEEE single and double precision FP (32 and
64 bits) and an 80-bit extended precision mode. PowerPC FPUs support
single and double precision.
SSE/SSE2 has 128-bit short vector registers, same as AltiVec. SSE2
can actually do some things AltiVec cannot (supports 2-wide 64-bit
double precision and 2-wide 64-bit integer operand formats).
-- Tim Seufert
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