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Old 2003-07-31, 12:30   #1
dsouza123
 
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Default What will an AMD Opteron be classified as ?

What will an Opteron show up as on Prime95 using Options/CPU ?
AMD Athlon or Opteron or even P4 because it has SSE2 support.
Display for older versions of Prime95 and the most current.

Which code path will it use ? Athlon,P3 or P4
The Opteron has SSE2 but could be viewed as an Athlon.
Or will the CPU features be the deciding point ?

For trial factoring it could use FP for up through 2^64 and SSE2 above.

Also in http://mersenne.org/primenet/summary.txt
will a new category AMD Opteron be added ?
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Old 2003-08-01, 03:30   #2
QuintLeo
 
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I would guess that the Opteron would be picked up as an "unknown CPU" - kinda like Athlons were up to somewhere in the late 22.x or early 23.x series clients.

Per the benchmarks I've seen posted around the Web, Opterons DO take advantage of the SSE2 stuff - though their clock is so much slower than high-end P-IVs/Xeons they are STILL significantly slower. That might change some if/when George gets the change to work with one long enough to provide Opteron-specific enhancements, but I suspect they'll still lag some due to the clock speed advantage - unless they ramp up faster than the P-IV/Xeon manages.

I dunno what it does on trial factoring - since it has SSE2, I'd guess it does the standard P-IV/Xeon type split between integer and SSE2 code.
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Old 2003-08-01, 16:37   #3
ewmayer
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A related question - if one is manually setting the CPU type in the .ini file, does the SSE2-based FFT only kick in for CPUType = 12? (i.e. numerical code for the P4)
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Old 2003-08-02, 03:19   #4
dsouza123
 
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From the following post in Hardware
The effect of SSE2 in P4s
http://www.mersenneforum.org/viewtopic.php?t=496

cmokruhl10 wrote
Quote:
To disable SSE2, I put "CpuSupportsSSE2=0" in local.ini.
CpuSupportsSSE2=1 in local.ini should enable it.

Prime95 may use SSE2 depending on the CPU features only
( if it detects the features at runtime,
if not (just info in a table) then either
the CpuSupportsSSE2=1 or the type 12 for P4 is needed )

What really determines what hardware features are used/code path run ?

Is it runtime detection of CPU features ?
Is it settings in local.ini ?
Is it some combination with overides ?
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Old 2003-08-02, 14:29   #5
Prime95
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Prime95 will use SSE2 if CPUID reports that it is supported AND running a sample SSE2 instruction does not cause an error AND local.ini has not overridden the decision with CpuSupportsSSE2=0

In general CPUID governs the LL and factoring code path, but you can override using local.ini
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