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SubjectRe: 3DNow! patches on Winchip.
On Thu, 30 Dec 1999, Alan Cox wrote:

> Make sure you benchmark both the cached and uncached cases.

I did a test copying large amounts of memory around in 64kb chunks..

Cached:
3dnow : 25 secs
integer : 3 minutes

Non-Cached:
3dnow : 75 secs
integer : (Still running on another box after ~15 minutes)


> If it is definitely a win to use the 3dnow code then use it.

I think the above figures speak for themselves.
Remember, I'm not running this on the correct bus speed, so the
proper benchmark will probably be much higher.

> Note that there is some stuff pending (hopefully for 2.4.0) that
> allows you to plug in multiple memcpy routines and handle the choice
> per cpu.

That sounds great.
How will these be selected, by an extra menu in the config ?

> That will also allow you to do finer tuning for the winchip.

Since my initial posting, I read that on the the Winchip 2A the prefetch
instruction is treated as a nop. Eliminating these from the routine gains
a few more benchmarks. Would that then make it the same as the MMX-copy ?

> Right now with the current draft of that code it has support for

Is this already in 2.3.x ?

regards,

Dave.


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