[Tfug] CPU Query

[Sean Warburton]

I have an old Intel P4 3.6 GHz CPU I will sell for $65. (It's a 660).You can
overclock it like crazy ( i got it to 4.6 on liquid). It's got
Hyper-Threading and 4 megs of Cache (2 MB for each logical core). It
can calculate PI out to a million digits in about 30-something seconds.
         Sean


On 3/31/07, Jim Secan <jim at nwra.com> wrote:
>
> > I assume you mean to imply that your tasks
> > are "compute-bound" and not I/O-bound?  Do you
> > have enough awareness of what the actual algorithms
> > entail (e.g., fixed point vs. floating point, etc.)
> >
> > --don
>
> I wrote all the code, so I know exactly what it's doing (OK, so I didn't
> write the SVD package, but that's from one of the optimized libraries).
> I/O has all been optimized such that so you read it all in (binary
> unformatted), crunch numbers, and then write it all out.  The "bind" is in
> floating-point operations (mostly matrix manipulations - this is a largish
> inverse problem).  My interest is in whether the OS can take advantage of
> the 2X CPUs without my having to get a compiler (Fortran) that will do
> this.  Either that, or get into the manual "loop unrolling" business,
> which loses me more (in my time) than I would gain.  I want to know if
> paying a little more for a 2X CPU will gain me in throughput without my
> having to do anything other than copy codes over from my current FC3
> system and go.  As a related side issue, I could care less about video
> performance - I work at the command line and could live with this on a TTY
> user interface.
>
> I have heard that some OS's (distros) will do a sort of load-leveling, but
> I don't know what sort of gain this would provide for a single process.  I
> have doubts about that, and that's why I'm asking.  I certainly don't want
> to find that I pay more for a 2X only to find that my processing runs
> slower than a comparable speed (and cheaper) 1X because I gain nothing
> from the second processor and lose from extra things the OS is doing
> because it knows it has more than one processing path through the CPU.  I
> have seen this sort of thing happen to people trying to parallelize or
> vectorize their codes.  Definitely a YMMV situation (and possible also a
> TANSTAAFL situation RE gain without pain).
>
> Thanks.
> Jim
>
>
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