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Old 2009-12-15, 23:25   #1
mack
 
Sep 2009

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Default What does the gHz credit actually mean?

What does the gHz credit actually mean?
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Old 2009-12-15, 23:52   #2
Mini-Geek
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"Tim Sorbera"
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It's a rough measurement based on how much work a reference CPU (I think a Pentium 4) could get done in a day if it were clocked at 1 GHz. If by "mean", you mean "does it have any practical usage", no, it's just a way to measure how much work something is and rank people appropriately..
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Old 2009-12-16, 04:18   #3
petrw1
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Quote:
Originally Posted by Mini-Geek View Post
It's a rough measurement based on how much work a reference CPU (I think a Pentium 4) could get done in a day if it were clocked at 1 GHz. If by "mean", you mean "does it have any practical usage", no, it's just a way to measure how much work something is and rank people appropriately..
I believe it is a theoretical 1 Ghz core of a Pentium Duo.
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Old 2009-12-16, 09:32   #4
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From George's post in the "PSI, mpg, GHz P4-days an P90 years" thread at http://www.mersenneforum.org/showpos...07&postcount=3

Code:
// In Primenet v4 we used a 90 MHz Pentium CPU as the benchmark machine
// for calculating CPU credit.  The official unit of measure became the
// P-90 CPU year.  In 2007, not many people own a plain Pentium CPU, so we
// adopted a new benchmark machine - a single core of a 2.4 GHz Core 2 Duo.
// Our official unit of measure became the C2GHD (Core 2 GHz Day).  That is,
// the amount of work produced by the single core of a hypothetical
// 1 GHz Core 2 Duo machine.  A 2.4 GHz should be able to produce 4.8 C2GHD
// per day.
//
// To compare P-90 CPU years to C2GHDs, we need to factor in both the
// the raw speed improvements of modern chips and the architectural
// improvements of modern chips.  Examining prime95 version 24.14 benchmarks
// for 640K to 2048K FFTs from a P100, PII-400, P4-2000, and a C2D-2400
// and compensating for speed differences, we get the following architectural
// multipliers:
//
// One core of a C2D = 1.68 P4.
// A P4 = 3.44 PIIs
// A PII = 1.12 Pentium
//
// Thus, a P-90 CPU year = 365 days * 1 C2GHD *
//               (90MHz / 1000MHz) / 1.68 / 3.44 / 1.12 
//             = 5.075 C2GHDs
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Old 2009-12-16, 12:30   #5
R.D. Silverman
 
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Quote:
Originally Posted by mack View Post
What does the gHz credit actually mean?
Does anyone remember Firesign Theatre?

"What do it mean, Mr. Natural?"

"It don't mean shit, boy".
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Old 2009-12-17, 10:41   #6
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Quote:
Originally Posted by mack View Post
What does the gHz credit actually mean?
Another way to look at it is as 2 flops/cylce so each ghz-day is 172,800,000,000,000 ( 1.728E+14 ) floating point operations (multiplies mostly I think) regardless of the speed of the machine.

Last fiddled with by lfm on 2009-12-17 at 10:50
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