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Technology Stocks : Advanced Micro Devices - Moderated (AMD)
AMD 214.87-0.1%3:59 PM EST
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To: Joe NYC who wrote (105857)11/14/2003 7:39:47 PM
From: PetzRead Replies (1) of 275872
 
re: AMD extends these [MMX instructions] a bit apparently.
PADDQ page 84 - can add 2 64 bit integers
PSUBQ page 232 - you can guess.

Do these extensions only work in long mode?

I guess my overall point about 64-bit extensions is that adding registers and instructions is something relatively easy for an OS to handle -- it doesn't have to use the instructions and it just has to save and restore registers if a context change occurs when the software is executing in the extended mode. But adding 64-bit addressing is a whole nuther ball of wax, and that may be where Microsoft drew the line.

the downside is that these instructions don't participate in program flow the way normal registers do. They need to be moved to MMX registers, and moved back all the time, can't be used in comparisons, as indexes to arrays, or counters etc.

Could Intel's extensions do everything AMD64 does *except* 64-bit addressing? The obvious question would be, Why do such a thing?
1) Preserve Itanium
2) cache design and chipset design doesn't have to change
3) would always be easy to go 100% AMD64 at some future time

Problem: memory allocation in 64-bit-extended-Windows would have to be different for Intel than AMD.

Just thinking out loud.

Petz
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