Messages in this thread |  | | From | Jason Flynn <> | Date | Thu, 6 Feb 1997 13:40:02 +0000 | Subject | Re: MMX for kernel |
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Hi, <stefan> > Hmm. I've been thinking about this, and since MMX instructions use the > FPU data paths, I'm not sure it's such a good idea to use MMX instructions. > I read somewhere that some special instruction is used to kind of > 'switch' between MMX and FPU mode, and that this takes some 50 cycles. > Now, wouldn't that mean that we'd waste a lot of time here, > for instance, if some programs make heavy use of FPU and at the same time > makes a lot of system calls involving MMX instructions? </stefan>
I not sure but : isn't it the process of clearing the registers (cos MMX and FPU use the sam ones) and clearing the pipeline that takes these cycles ? And surely this would be done anyway during task switching so the only extra overhead is if you mix types within one task.
Probably wrong, J ------------------------------------------------------ Any opinions expressed in this message are entirely my own and may not reflect the opinions of my employer. ------------------------------------------------------ I know you believe you understand what you think I wrote. But I am not sure that you realise that what you read is not what I meant. ------------------------------------------------------
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