Iteration times in i5 and i7 - Page 3

Jud McCranie · 2013-08-07, 20:47

Well, i don't understand it exactly, but I added the fourth stick of memory and now I'm getting 19ms on three workers on the i5.

Recap: At first I was getting 22ms on four workers. I added some software (only Firefox and Thunderbird, I think) and set some things, making sure it would not sleep or hibernate. A few hours later it went up to 40ms. Then it went back to 22. Then it went back to 40.

I checked my memory, and slot #2 was empty - #1, 2, and 4 had sticks. I rearranged the sticks, now #4 was empty but the matching pairs were not in the same color of slot. Still got 44. I rearranged the memory to put matching pairs in the same color and leave #4 empty. Still 40ms. And four workers was getting less throughput than two or three, so I cut it to three workers, and the iteration time dropped to 29. Quite a but worse than I had been getting.

So today I added the fourth stick, and now I'm getting 19ms on three workers. So the memory arrangement must have had something to do it, but it was fluctuating from 22 to 40 when I didn't make any changes. (It would be one for a while then the other - then only 40.)

So now it seems to be OK and is pretty much matching my SB i7, which runs at 3.4GHz vs. 3.0.

Primeinator · 2013-08-07, 22:31

Quote:

Originally Posted by Jud McCranie

My Sandy Bridge i7 is running about 73C running three workers. With four workers it was about 78C. With four workers, the fan was on a higher speed. At 73 the fan doesn't run nearly as loudly, but louder than the IB i5.

Quote:

Originally Posted by TheMawn

Heat: AMD's latest get pretty prissy around 60C. My Ivy Bridge is running in the mid 70's. Throttling happens at 105C. Which is good because Ivy Bridge runs 10C-15C hotter than it needs to.

So 51-54 Celsius is nothing on a i7 Sandy Bridge? My quad is running four workers. It apparently automatically overclocks to 3.8 GHz (normal is 3.6) and is running at about 21 ms for 55.6 M exponents.

TheMawn · 2013-08-07, 23:46

Mid 50's is great on Sandy Bridge, Ivy Bridge and Haswell, too, I should think. You have a lot of overclocking headroom if your CPU is a k-series and your motherboard can handle it.

My mid 70's is an i5-3570k running at 4.6GHz on four cores, four threads.

Jud McCranie · 2013-08-07, 23:55

I've never overclocked. I wonder about the advisability of it - it it causes the system to miss one bit, that ruins your result.

TheMawn · 2013-08-08, 04:34

My CPU, in its current settings, is 72-hours stable using the torture tests. 4.7GHz was also, but it required significantly more voltage than I am comfortable with at the moment, and I could not get the settings to stick no matter what I did. 4.8GHz caused all of the weirdest things to crash, like windows Aero despite it being heavily dependent on graphics.

It's all relative. Stock settings aren't 100.0000000% perfect either. Run some double check LL's also if you're worried. Or leave the settings at stock. According to an old rule of thumb, which says that you half the lifespan of your CPU by a half for every 10C hotter you operate it, your CPU should outlast mine four times.

Jud McCranie · 2013-08-08, 14:18

Quote:

Originally Posted by TheMawn

My CPU, in its current settings, is 72-hours stable using the torture tests.

But is there a point where errors start to creep in before it gets unstable? A one-bit error can ruin a week of work. I'm thinking of the old adage "Do you want it done quickly or done right?"

chris2be8 · 2013-08-08, 15:42

Quote:

Originally Posted by Jud McCranie

Recap: At first I was getting 22ms on four workers. I added some software (only Firefox and Thunderbird, I think) and set some things, making sure it would not sleep or hibernate. A few hours later it went up to 40ms. Then it went back to 22. Then it went back to 40.

With two paired memory sticks and one not paired run times would vary with how much real memory the task got from the paired sticks and how much from the unpaired stick since that would be slower. That's the most likely explanation I can think of for the varying run times.

Chris

Jud McCranie · 2013-08-08, 15:56

Quote:

Originally Posted by chris2be8

With two paired memory sticks and one not paired run times would vary with how much real memory the task got from the paired sticks and how much from the unpaired stick since that would be slower. That's the most likely explanation I can think of for the varying run times.

Chris

Yes, but the first day it changed drastically and I did nothing to the memory. I think all I did to the computer other than starting Prime95 was install Thunderbird and Firefox and update Windows 7. (I'm not sure what order I did those things.) But maybe for some reason it was using one bank of memory and then the other.

BTW, about 18 hours after adding the fourth stick it is still getting good performance.

TheMawn · 2013-08-09, 00:43

Quote:

Originally Posted by Jud McCranie

But is there a point where errors start to creep in before it gets unstable? A one-bit error can ruin a week of work. I'm thinking of the old adage "Do you want it done quickly or done right?"

The torture test runs preset tests. It runs x number of iterations of exponent y using FFT length z and knows the answer you should get. Your one-bit error is enough for the program to detect an error.

Jud McCranie · 2013-08-09, 00:55

Quote:

Originally Posted by TheMawn

The torture test runs preset tests. It runs x number of iterations of exponent y using FFT length z and knows the answer you should get. Your one-bit error is enough for the program to detect an error.

That should do it. You say that you run the torture test for 72 hours?

I looked up some videos about overclocking i5 and i7, and it may be more involved than I want to get into.

Jud McCranie · 2013-08-09, 03:36

I looked at more overclocking videos, and it looks like a lot of work. If there was software to do it more automatically, I'd probably try it.

Anyhow, before I added the fourth memory stick I was getting lower total throughput with four workers than two or three, so I switched to running three. With the other memory stick, four workers does give the best throughput. I was getting 19ms with three workers and now 22ms with four, so the fourth one increases throughput only 15%.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
What are your per-iteration times?	LiquidNitrogen	Hardware	22	2011-07-12 23:15
CPU frequency and iteration times.	rx7350	Hardware	12	2006-05-08 21:54
LLR.exe FFT crossovers and iteration times	SlashDude	15k Search	0	2004-01-28 05:47
slow iteration times	PLeopard	Hardware	9	2003-10-29 05:48
Slow iteration times with 23.7	smoffat	Software	13	2003-10-22 22:50

2013-08-07, 20:47	#23
Jud McCranie Oct 2007 2×3²×5 Posts	Well, i don't understand it exactly, but I added the fourth stick of memory and now I'm getting 19ms on three workers on the i5. Recap: At first I was getting 22ms on four workers. I added some software (only Firefox and Thunderbird, I think) and set some things, making sure it would not sleep or hibernate. A few hours later it went up to 40ms. Then it went back to 22. Then it went back to 40. I checked my memory, and slot #2 was empty - #1, 2, and 4 had sticks. I rearranged the sticks, now #4 was empty but the matching pairs were not in the same color of slot. Still got 44. I rearranged the memory to put matching pairs in the same color and leave #4 empty. Still 40ms. And four workers was getting less throughput than two or three, so I cut it to three workers, and the iteration time dropped to 29. Quite a but worse than I had been getting. So today I added the fourth stick, and now I'm getting 19ms on three workers. So the memory arrangement must have had something to do it, but it was fluctuating from 22 to 40 when I didn't make any changes. (It would be one for a while then the other - then only 40.) So now it seems to be OK and is pretty much matching my SB i7, which runs at 3.4GHz vs. 3.0.

2013-08-07, 23:46	#25
TheMawn May 2013 East. Always East. 11×157 Posts	Mid 50's is great on Sandy Bridge, Ivy Bridge and Haswell, too, I should think. You have a lot of overclocking headroom if your CPU is a k-series and your motherboard can handle it. My mid 70's is an i5-3570k running at 4.6GHz on four cores, four threads.

2013-08-07, 23:55	#26
Jud McCranie Oct 2007 5A₁₆ Posts	I've never overclocked. I wonder about the advisability of it - it it causes the system to miss one bit, that ruins your result.

2013-08-08, 04:34	#27
TheMawn May 2013 East. Always East. 11×157 Posts	My CPU, in its current settings, is 72-hours stable using the torture tests. 4.7GHz was also, but it required significantly more voltage than I am comfortable with at the moment, and I could not get the settings to stick no matter what I did. 4.8GHz caused all of the weirdest things to crash, like windows Aero despite it being heavily dependent on graphics. It's all relative. Stock settings aren't 100.0000000% perfect either. Run some double check LL's also if you're worried. Or leave the settings at stock. According to an old rule of thumb, which says that you half the lifespan of your CPU by a half for every 10C hotter you operate it, your CPU should outlast mine four times.

2013-08-09, 03:36	#33
Jud McCranie Oct 2007 132₈ Posts	I looked at more overclocking videos, and it looks like a lot of work. If there was software to do it more automatically, I'd probably try it. Anyhow, before I added the fourth memory stick I was getting lower total throughput with four workers than two or three, so I switched to running three. With the other memory stick, four workers does give the best throughput. I was getting 19ms with three workers and now 22ms with four, so the fourth one increases throughput only 15%.