Re: Alpha 21264.

[Jeff Sturm <jsturm@xxxxxxxxxxx>]

On Wed, 13 Jan 1999, Andy Almond wrote:
> Three questions relating to the 21264 CPU and 264DP motherboard.
> 
> (a) I haven't used a dual processor before, so how much performance can you expect over a single CPU machine when working on a single job using an SMP linux kernel. Can you configure the system to use both CPUs for an ordinary job, or does that require a special compilation option/re-coding?

SMP works well for parallelized tasks, however for a single process 
running a single thread, one CPU will be basically idle.

To take advantage of SMP, you can run multiple processes concurrently, or 
design your process for multithreading (using pthreads or similar).

> (b) Are DEC fortran/C ev6 compilers going to be available under linux? or is DEC UNIX or NT the only way to achieve this? I assume that the performance of gcc will be relatively poor compared with DECs C compiler, as is the case for the 21164 processor.

GCC does reasonably well at integer code.  Most FP-intensive code relies 
heavily on math libraries, which are improving on Alpha/Linux thanks to 
libffm.   It's still not as fast as the DEC compiler, but it isn't dismal 
either.

> (c) Will code already compiled for ev56 CPUs run efficiently on an ev6 CPU?

Good question.  I have heard that the ev6 can do its own instruction 
scheduling.  If that's true, I'd speculate that the ev6 can partly 
compensate for poor instruction scheduling in the compiler, and perhaps 
improve ev56 object code too.  Anyone know for sure?

Jeff

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