Alex Gibson wrote:
> "JJ" <[email protected]> wrote in message
> news:[email protected] oups.com...
> > Toms HW recently did a review on the DualCore D805 (around $150 or
> > less) which can be highly overclockable from 2.6Ghz with stock fan to
> > 3.6Ghz with Zalman cooler and even 4.1GHz with water cooling which was
> > then able to beat out the >$1K Extreme edition 965 and the AMD Athlon
> > 64 FX-60 on gaming benchmarks. That article lead to a good run of sales
> > for that chip.
> >
> > http://www.tomshardware.com/2006/05/..._41_ghz_cores/
> > http://www.tomshardware.com/2006/06/...g_rig_for_720/
> >
> > Intel locked out cpu overclocking, but left in FSB modding. Nominal
> > power is 90W, but at 4.1GHz it went to 200W, takes some nerve to try
> > that.
>
> But is it worth risking over clocking on this sort of work load ?
Depends, these days a cpu lasts what 18 months before a replacement
cycle esp in high end engineering. If you "Burn" a cpu by overclocking
you possibly reduce the full unused lifetime from several years down a
bit, but still it should easily make it through the first 18 months.
>
> How do you know you are not getting errors in the generated bitstream ?
> How do you know what errors (if any) get introduced as the cpu is running
> out of spec?
>
One can always diff the files for test cases compiled on a slow normal
and overclocked cpu. assuming 2 different cpus should create the exact
same bitfile for same setup.
Actually it isn't really running out of spec. If you read the 1st
article (it was a very long article though 40+ never ending pages) you
would see that most of the cores for these Intel Duo core cpus are very
similar and have some varying margin. Intel has to sell the same basic
design at different price points so for some families they fix the
clock multiplier to prevent cheapskates from overclocking while selling
the same basic design in the Extreme edition with a few more options.
The article explains exactly why the FSB can be so easily overclocked,
it starts off at 133MHz instead of 200MHz or 266Mhz in the higher
priced parts. The multiplier seems to be in fractions with 7 or 8 steps
to double it to the top of the line case. As long as the DDR ram is
also 533MHz. To get past the Zalman cooler at 3.6Ghz, they rigged the
voltage as well as water cooled, thats way past my comfort level.
I wouldn't ever recommend overclocking on a part that has no margins
such as top of the line chips. Overclocking has always been done on
parts that were marketed as low end chips that were much closer to high
end chips than Intel let on, although the cache might be smaller in
that case. Some of the first Celerons were classic overclockers.
> Maybe fine overclocking your own home machine for gaming or whatever but not
> a work machine.
>
>
> Alex
Ordinarily I'd agree with that, I would rather have quiet than turbo
jet so I haven't done this yet. In an office situation, I wouldn't
recomend water cooling under most peoples desks, but a shared server
machine with half the compute time might be tempting.
If a cheap solution can actually blow past the top of the line Intel or
AMD models which have no further room, I am open. The benchmarks
although gaming related, suggest upto 2x the performance with the water
rig, which is much better than the raw 2.66 to 4.1 suggests. The
performance is coming from the FSB speedup. That might well follow for
FPGA jobs as well. I wonder if we will ever know.
John Jakson