Author: Eugene Nalimov
Date: 15:58:51 02/15/00
Go up one level in this thread
I am not sure which processor that particular WinCE machine uses (there *are*
real 64-bit MIPS-compatible CPUs), but even for 32-bit 1-pipline CPU going to
64-bit data may be not so bad, if pipeline is deep enough (>= 5 stages).
Performance would be not 2 times worse, as you can think.
Very simple example: we have the following basic block, and everything is in
cache:
if (value1 & value2 == 0)
For 32-bit machine, with pipeline length 5, no speculative execution:
mov r1, [sp+value1]
mov r2, [sp+value2]
and r1, r2
cmp r1, 0
je label
9 clock ticks.
For 64-bit machine:
mov r1, [sp+value1]
mov r2, [sp+value1+32]
mov r3, [sp+value1]
mov r4, [sp+value1+32]
and r1, r3
and r2, r4
or r1, r2
cmp r1, 0
je label
13 clock ticks, not 18.
Difference decreases as pipeline length increases - and that is current trend
for all CPUs.
Eugene
On February 15, 2000 at 17:28:31, Tom Kerrigan wrote:
>On February 15, 2000 at 14:49:36, Ricardo Gibert wrote:
>
>>The Cassiopeia E-100 & E-105 have a 131mhz 64-bit MIPS CPU (no FPU, but it does
>>have separate cache for data & code) with 16Mb or 32Mb ram. On my E-100 I have
>>an additional 48Mb of Flash memory. In addition, the instruction set is designed
>>to produce executables that are more compact. Plenty of memory for Crafty.
>
>Yeah, I guess it might have enough memory.
>
>But I'll have to call you on the 64-bit CPU... I suspect it's approx. an R4000,
>32 bit, 1 pipeline, 4kb cache. Similar to the one in the PlayStation.
>
>-Tom
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