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Old 2009-04-28, 10:12   #1
cipher
 
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Default Should i go with i7 920 or Q6600?

I am planning to build a dedicated PC for LLR for NPLB. On few forums i am hearing whispers how LLR doesn't get along with i7 cores. Also with HT enabled on i7 cores will i get 8 cores instead of 4 cores on Q6600.

Will the crunch output be the same, for LLR on Q6600 vs i7 920 (despite being 8 cores due to HT) the iteration time will drop on i7?

Any input or advice will be greatly appreciated.

Thanks in advance.
Cipher
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Old 2009-04-28, 10:25   #2
MyDogBuster
 
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Quote:
I am planning to build a dedicated PC for LLR for NPLB. On few forums i am hearing whispers how LLR doesn't get along with i7 cores. Also with HT enabled on i7 cores will i get 8 cores instead of 4 cores on Q6600.

Will the crunch output be the same, for LLR on Q6600 vs i7 920 (despite being 8 cores due to HT) the iteration time will drop on i7?

Any input or advice will be greatly appreciated.

Thanks in advance.
Cipher
I run both a Q6600 and an i7 920. Neither is overclocked. A test that takes me 180 secs on a Q6600 takes me 280 secs on the i7 (assuming all 8 cores are running). The test on the i7 will be 170 secs if it runs by itself. So it looks like you get the equivalent of almost 6 Q6600 cores on an i7-920. I do have all 8 cores running with no problems.

Q6600 is 2.4ghz 3 GB DDR2
i7 is 2.66ghz 6GB DDR3

Last fiddled with by MyDogBuster on 2009-04-28 at 10:28
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Old 2009-04-28, 10:29   #3
cipher
 
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Thanks clarifies a lot.
I can get 2 Q6600 systems for the price of 1 i7 920 clear choice for now is 2 Q6600 systems, unless you think otherwise.

thanks cipher

p.s: In my calculation i7 920 is only 28% faster.
(WU = Work Unit (an approximation)

Lets say you have 1000 seconds time limit.
1 WU on i7 920 running all 8 cores takes 280sec
so we get 1000sec/280sec (per core) = 3.57WU in 1000 sec * 8 core = 28.57 WU done on i7 920 1000 seconds

1 WU on Q6600 running all 4 cores takes 180 sec
so we get 1000sec/180 (per core) = 5.55 WU in 1000 seconds * 4 cores = 22.20 WU done on Q6600 in 1000 seconds

((28.57WU-22.2WU) / 22.2 WU) * 100 = i7 920 is 28.69% more efficient.

Last fiddled with by cipher on 2009-04-28 at 10:37
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Old 2009-04-28, 10:37   #4
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Quote:
Thanks clarifies a lot.
I can get 2 Q6600 systems for the price of 1 i7 920 clear choice for now is 2 Q6600 systems, unless you think otherwise.

thanks cipher
Thats what I would do but then again, I don't overclock. Maybe some folks who do, might have a different opinion. I also use KVM switches and having an i7 leaves a slot open for another machine. Tough call actually.
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Old 2009-04-28, 10:52   #5
fivemack
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I know Earth Day was some time ago, but I would point out that two Q6600 systems would use probably 400 watts, and one i7/920 uses about 250 (I have both kinds of systems and a power-meter); I would also consider the Phenom II, which in my experience uses slightly less power and is a bit faster than a Q6600, and also allows rather cheaper integrated-graphics motherboards.

A watt is a dollar a year, so over three years you're paying $450 more to run two Q6600s.
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Old 2009-04-28, 14:42   #6
IronBits
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The I7-920 easily overclocks to 3.5GHz and rock stable with only changing the 'fsb', making it a clear winner over Q6600. (with quality 3rd party HSF)
I upgraded my entire Q6600 collection to I7s.
I save on 1/2 the heat output and electricity and the A/C unit doesn't have to work as hard.
I complete more work with 1/2 the computers I used to have.

Last fiddled with by IronBits on 2009-04-28 at 14:45
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Old 2009-04-28, 14:57   #7
petrw1
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Quote:
Originally Posted by MyDogBuster View Post
A test that takes me 180 secs on a Q6600 takes me 280 secs on the i7 (assuming all 8 cores are running).
I must have missed the meeting.

What I have read tells me the i7 is a Quad-Core with Hyperthreading to make it LOOK LIKE it has 8 cores. My PIV is a single core with HT making it look like 2 but there is still only 1 core and if I try to run 2 workers (no matter what I have them doing) I either get the same or worse total thruput than running 1 worker.

OR does the i7 do something cool to get more out of HT?

Last fiddled with by petrw1 on 2009-04-28 at 15:00 Reason: OR...
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Old 2009-04-28, 15:13   #8
IronBits
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I7 is a 4 core cpu without HT.
I7 shows 8 cores with HT turned on.
I7 with HT enabled does the about same amount of work as ~6 real cores.
It also overclocks very easily to 3.5GHz, effectively producing about the same amount of work of 2 Q6600 quad cores.

Last fiddled with by IronBits on 2009-04-28 at 15:16
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Old 2009-04-28, 15:16   #9
fivemack
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The i7 core has rather more resources to share among the two threads than the P4 had, which means that running two jobs on two threads takes in my limited experience about 1.5 times as long as running one job on one thread, rather than about twice as long as with the P4.
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Old 2009-04-28, 15:24   #10
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Yes the HT on the i7 does make a difference.
They get 15C hotter :)

Actually HT does on the P4 as well but they had poor memory throughput so some clients didn't benefit from having 2 run at once.

I also will be replacing all my old 65nm quads with i7.

Last fiddled with by PCZ on 2009-04-28 at 15:27
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Old 2009-04-28, 15:30   #11
Flatlander
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Quote:
Originally Posted by PCZ View Post
I also will be replacing all my old 65nm quads with i7.
Let me know if you are putting them in a skip.
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