Don’t kid yourself – personal computer industry pundits are talking of Intel Corp’s release today of the P55C Pentium with the MMX multimedia instruction set leading to Christmas in January but very very few people have large amounts of spare cash left for major discretionary expenditures after the turn of the year, and the MMX set is overwhelmingly of more interest in the home than the business market. Nevertheless, no-one can afford to be out of the market, so all the major personal computer manufacturers have MMX machines lined up and ready to fly off the shelves today. However, Intel is not being too greedy with the MMX Pentiums. Word is that the parts will come in 166MHz and 200MHz versions for the desktop market and 150MHz and 166MHz versions for mobile computers, with the desktop chips at $407 and $550 for 1,000-up and the mobile ones are $443 and $550. And as well as MMX, you also get the on-chip cache doubled to 32Kb and more efficient branch prediction. However, instead of having its own registers, the MMX instruction bank uses the floating point registers, which makes it rather important that programmers remember to save the state of the registers each time before switching between instruction sets. A further problem apparently arises when switching from the MMX set back to the floating point set that unless the programmer remembers to flush the registers after the last MMX instruction has been executed, the first floating point instruction can begin operating on the MMX leftovers.
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