On 19 Jun 00, at 18:33, Lawrence Murray wrote:
> I find it amusing that you do think a 550mhz too slow.
Too slow _for 10 million digit numbers_. PIII-550 is fine for
"ordinary" LL tests & is faster than any of my systems except the
Athlon 650. If nothing else was available, then there would be a
valid excuse - but there are now a great many systems around which
are significantly faster than a PIII-550.
> But its attitudes like this that make me want to save the
> 20-30 a month in electricity and just shut them down....
That's not what I meant at all!
> But I realize that
> every cpu cycle does advance the cause.
Yes. But random errors can and do occur and the probability of one
occurring in any given time interval is independent of the CPU speed.
Therefore one wants to keep run times reasonable.
If you get one glitch during one year & you're processing an exponent
in the 33 million range, all your work is wasted. If you're
processing exponents in the 10 million range instead, you will
complete about 10 assignments and 9 of them will be OK. The same
argument applies for any error rate except zero (unattainable) and
>= 1 per CPU cycle (repair or replace the system!)
To make the most effective use of _any_ system you need to choose its
work carefully.
I'm still running DC assignments on a P100 & will continue to do so
as long as I can get assignments under 5.25 million (~6 weeks run
time). Similarly I'll move my pair of PII-350s from LL testing to
double checking when I can no longer get assignments under 10.32
million.
> In order to keep a state of the art computer working on this
> project one would need to buy a new computer every 3 months.
Probably every 3 weeks rather than every 3 months ;-(
I'm running a number of systems, few of which were anywhere close to
"state of the art" even when new; I try to maximize useful cycles per
dollar rather than raw speed. Personally I think it's absurd to pay 4
times as much for a 1GHz Athlon as you would for a 700 MHz Athlon,
which has a lot more than 1/4 the performance. But I do consider it
worth paying extra for reliability-related features like extra
cooling fans, ECC memory and UPS to protect the system from
inevitable irregularities in the mains (utility) power supply.
Regards
Brian Beesley
_________________________________________________________________
Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm
Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
