George Woltman wrote:
> SMT for those that don't know makes one P4 CPU look like 2 CPUs
> to the operating system.  Each "virtual CPU" has its own set of registers
> and each runs a different program (actually a different "thread").  The real
> CPU can now execute instructions from either virtual CPU.


SMT on Intel? I didn't know about that.

If SMT is implemented like the planned Alpha EV8 implementation, then it will be up to 
the OS to schedule multiple tasks for the processor. Consequently unless the OS had 
special interfaces to allow one program to consume several SMT slots, the program 
would either be restricted to running as normal, or have to try running as several 
processes, or would have to replicate the necessary OS kernel functionality itself 
(difficult, and not portable).

I think the odds are that prime95 / mprime would not be able to gain much unless 
either the OS makes special arrangements for single compute-intensive programs, which 
seems unlikely since SMT is intended for CPUs running multiple processes, or the OS is 
open source and can be patched at kernel level, which excludes windows.

Some SMT news that I know of:
Alpha EV8 will have SMT with 4 simultaneous execution paths.
Alpha recently got canned by compaq, so the above may never happen.

Yours,

======= Gareth Randall =======

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