Quad core weigh up help

[ewmayer]

Originally Posted by lavalamp

Heh, OK, nevermind about that Barcelona then. A shame really, the quad precision would have been interesting to play with, not that I'm all that great with C.

Quad precision?

[lavalamp]

If I'm understanding it right, yes, though I'm open to correction:

Originally Posted by http://en.wikipedia.org/wiki/AMD_K10

As with the server chips codenamed Barcelona, the new desktop quad core series will feature a shared L3 cache, 128-bit floating point (FP) units and an enhanced microarchitecture.

[ewmayer]

Originally Posted by lavalamp

If I'm understanding it right, yes, though I'm open to correction:

Yes, based on the wording you quote one would be led to believe they are referring to quad-precision FP.

But in fact they're talking about double-pumped 64-bit FP, e.g. via the SSE2+ instructions - just like the Intel Core2 architecture has.

Genuine hardware support for quad-precision FP simply has too small a market-segment-of-interest to be worth doing, at least for the foreseeable future. If you need quad floats, you do as ever, emulate in software and throw hardware at large problems needing this precision.

[cypherplex]

With my new AMD Phenom 9850 B3-stepping i got this at 4x2750MHz:

My quad-core combination 24/7 is:
Core 0 - LL Testing
Core 1 - LL Testing
Core 2 - LL Testing
Core 3 - LL Testing

Below is a report on the work you have queued and any expected completion
dates.
[Worker thread #1] M41335781, Lucas-Lehmer test, Fri Oct 31 11:44 2008
[Worker thread #2] M38618729, Lucas-Lehmer test, Thu Oct 9 04:01 2008
[Worker thread #3] M41336749, Lucas-Lehmer test, Fri Oct 31 17:03 2008
[Worker thread #4] M41337059, Lucas-Lehmer test, Mon Oct 27 08:53 2008

Powerconsuption is: Ubuntu-Desktop, idle => 120W (primary)
Ubuntu-Desktop, 4xLL-tests 190W (primary)
MoBo is: ASUS M3A78 PRO (vga: AMD 780G chipset), 4GiB DDR2-1067 DRAM, be-quiet 430W PSU

Not bad eh?

Phenom 9850 B3 mprime - Benchmarks see here: http://www.mersenneforum.org/showthr...446#post139446

[stars10250]

-----
[Worker thread #1] M41335781, Lucas-Lehmer test, Fri Oct 31 11:44 2008
[Worker thread #2] M38618729, Lucas-Lehmer test, Thu Oct 9 04:01 2008
[Worker thread #3] M41336749, Lucas-Lehmer test, Fri Oct 31 17:03 2008
[Worker thread #4] M41337059, Lucas-Lehmer test, Mon Oct 27 08:53 2008
-----

This is interesting for comparison to my E8500. It runs 2 LL, 43M, in 28 days (therefore 4 LL would take 56 days). If you started Aug 17, your above results will take 75 days, 53 days, 75 days, and 71 days, respectively. The dual-core appears to be factoring larger numbers (43M vs. 41M) in considerably less time (56 days vs 70+ days). I haven't read much about AMD quad systems. Is this due to a memory bottleneck similar to what others have been reporting with the Intel quads?