Messages in this thread | | | Date | Thu, 10 Jul 1997 14:41:11 +1000 | From | Lawrence <> | Subject | Re: mmx support with smp |
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There is a 52-clock cycles when switching FPU and MMX mode.
I used procinfo to monitor a busy system and found that normally there is under 1,000 context switches per second. So, 52,000 clock cycles are used for that. For a 200Mhz MMX CPU, 52,000 / 200,000,000 = 0.026%. Mmmm....seems not that much :)
Lawrence
> But isn't there some other things going on insode the CPU re: FPU/MMX use? > If you context switch a task off a processor the is using MMX, then load > any other process expecting FPU setup... > > As I remember, there is a price (a heavy one) for switching back and forth > between MMX and FPU usage. The kernel may not be able to tell what mode > the application has put the CPU in. We shall see, I'm sure. > > (Doesn't the Tyan Tomcat III support two 166-MMX processors? All I remember > is the power warnings -- MMX processors draw more power than the non-MMX > cousins which causes problems for the Tomcat's as they were designed before > there was such a thing.) > > --Ricky
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