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Instruction Set Wars (debate)

post #1 of 3
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Just finished reading an interesting and detailed blog entry on forming a standards committee for cpu instructions. Similar to how we got the monster of C++ under control(only for hardware).
Some highlights of how inefficient modern cpu instruction sets have become:

1. The total number of x86 instructions is well above one thousand.
2. Today's microprocessors are still supporting even the most obscure undocumented instructions of the first 8086 processor from thirty years ago.
3. The costs of supporting obsolete instructions is not negligible. You need large execution units to support a large number of instructions. This means more silicon space, longer data paths, more power consumption, and slower execution.

4. If the undocumented codes had been eliminated then all instructions in the SSSE3 and SSE4 instruction sets would have a one-byte escape code rather than a two-bytes escape code.
5. Some processors have an extra stage in the pipeline only for rotating the x87 register stack
6. When the vector registers were extended from MMX to XMM, there was no plan for how to handle the predictable future extension to YMM. Instead we have the complexity of having two versions of every XMM instruction (one that zero-extends into the YMM register and one that leaves the upper part of the register unchanged)

A standardization committee could declare that standards-compliant software should not use a certain feature. Support for this feature could then be removed after e.g. ten years. If the standard says, don't use x87 and MMX registers, then we could replace all x87 instructions by emulation after a number of years.

Thoughts on forming this committee and how to improve/if instruction sets need improving?
WinTheFuture
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WinTheFuture
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post #2 of 3
Intel has almost always made the biggest changes to x86. I doubt that will change unless x86 falls out of fashion. Intel is too big and amd isn't in a position to push them at the moment.
     
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post #3 of 3
This explains why a lot of software isn't optimized for the newer instruction sets or AMD processors (intel's compiler). The only program I can think of off the top of my head that is optimized would be waterfox. We should sig this to help the issue get some recognition; I am.
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