Posted on 2004-11-04
Medium Priority
Last Modified: 2010-05-18

SSE2 has added packed instructions for integers.
Does this make the use of mmx obslete?

When should i use mmx or sse2?

Thank you.
Question by:hengck23
LVL 22

Accepted Solution

grg99 earned 1500 total points
ID: 12505732
Obviously, use them where they're going to do some good.

You also have to consider, do you want your program limited to run on only the newer machines that have the extra instructions?

First your program should check for the presence of MMX and/or SSE2, and/or their AMD equivalents.
The CPUID instruction returns a bunch of useful info about the current CPUs capabilities.

Then your program should mull over whether it can best do the hard inner loops using one or the other.

LVL 11

Expert Comment

ID: 12514633
In addition to grg99's answer, I would like to tell that
in contrast to MMX that is using existing CPU resources, SSE adds 8 independent 128-bit registers: XMM0 - XMM7.
And it allows you to solve MMX problems - you do not need commands like EMMS for switching modes.
Also SSe has additional 32-bit control/status register MXCSR.

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