Re: MMX performance....

Ingo Molnar (
Thu, 6 Feb 1997 15:43:17 +0100 (MET)

On Thu, 6 Feb 1997, Dale R. Worley wrote:

> From what I understand, everytime you switch between MMX mode and regular
> FP mode, 100 or so cycles are burned. If you are context switching
> alot (any multitasking enviornment), this would seem to add up.
> Assuming that the "cycles" are fundamental CPU cycles (as opposed to
> memory accesses, or something), that could take 1 microsecond or less
> (depending on your clock speed), which isn't much. [...]

2.1.25 does a system call in 150 cycles and context switches in 190 cycles
microseconds. Wanna add 100 cycles to each memory copy operation?

100 cycles are alot. And XFree86 is rendering fonts using the FPU. And we
have the pentium memcpy patch which uses the FPU for 64 bit wide memory

They should have made MMX a separate video subsystem chip. Ahh, no way,
then they couldnt call it 'the next pentium CPU'. And they couldnt patent
it as part of the x86 instruction set. damn.

-- mingo