Overclocking

Primeinator · 2013-08-13, 18:22

I possess an i7 3820 at 3.6 GHz; however, it appears to be automatically overclocking to 3.75 GHz without any action on my behalf. This I discovered from CoreTemp. For the purposes of LL testing, would I gain much benefit from overclocking further? Is this safe to do? Or is it better to keep it at its current level to avoid dramatically increasing the potential for error?

Other stats: 16GB DDR3 RAM at 2133 MHz.
High-performance cooling (temps pretty constant at 51-54)

Thanks!

lavalamp · 2013-08-13, 21:11

Sounds like the turbo is kicking in, that is the expected behaviour. It usually only does this when 1 or 2 cores are loaded and the others are idle.

I *think* with this CPU you can up the multiplier all the way to 43 (to give you 43 * 100 = 4300 MHz), which should be stable with a moderate (read: small) increase in Vcore. However if you do that make sure you run Prime 95 torture test and Intel Burn Core for a while to make sure.

Unfortunately, you cannot overclock your chip further as only the unlocked k models of Intel CPUs have such functionality.

When overclocking you would see essentially a linear scaling of performance with clock speed in all applications that aren't limited by some other aspect such as memory bandwidth/capacity, but it sounds like you're doing fine there with 16 GB of 2133 Mhz RAM (I assume dual channel, but if quad channel then woohoo!).

You CAN change the BCLK (base clock) to overclock further, but really really don't do that, it can cause all kinds of problems as that clock is used by all kinds of other chips on the motherboard and it can very easily cause your PC to become unstable.

The Sandy Bridge chips are fairly easy to overclock, and there are lots of guides around to help with things like voltages. As long as you keep the temps under control (sub 80 or 90 C), you should be fine.

Primeinator · 2013-08-13, 22:26

I am pretty sure it is dual channel. How do I confirm? A few quick Google checks do not help (much). My Computer ---> Properties only says 16 GB. Is there a way to tell?

TheMawn · 2013-08-13, 23:16

Your chip may not be very overclockable. It wouldn't surprise me if your chip isn't unlocked. On the other hand, it is an expensive chip for an expensive lineup, so maybe you CAN get it to at least 4300MHz which is definitely worth it if your cooling can handle it. You will need more voltage, and both frequency and voltage will contribute to extra heat.

The easiest way to tell if you're using dual or quad channel memory is to take off your computer's side panel and find the memory. It'll be near the top middle of your board. Check to see how many sticks you have and where they are. You should have four slots on either side of the CPU, and they should be two different colours. For example, you might have:

black - blue - black - blue - CPU - black - blue - black - blue

16GB is most likely going to be 4x4GB, though it might be 2x8GB and very unlikely to be 8x2GB. If you have eight sticks, you're set and using quad channel. If you have four sticks, make sure that they are all in the same coloured slots. They should therefore NOT be all on the same side of the CPU. If you have two sticks, make sure that they are again in the same coloured slots. This is dual channel.

The advantage of quad channel over dual channel is that your motherboard essentially sees the set of four sticks as ONE giant stick with four access points, and so quadrupled bandwidth. The "sets" are denoted by colours. This information should also be in your motherboard's manual if you have one.

A less experienced computer builder might have been tempted to slide the RAM sticks in sequentially:

black - blue - black - blue - CPU - DIMM - DIMM - DIMM - DIMM

Instead of the correct:

black - DIMM - black - DIMM - CPU - black -DIMM - black - DIMM

kracker · 2013-08-13, 23:32

Or another way to see if it really is on dual channel, just run CPU-Z and goto the Memory tab and it'll tell you a lot about your memory.

kladner · 2013-08-13, 23:32

Bingo! (Although TheMawn did explain the whole thing very well, too.)

Primeinator · 2013-08-14, 04:45

Thank you to everyone who posted. I appreciate both your willingness to answer my questions and your patience for my ignorance and lack of knowledge most of this forum perceives as highly rudimentary. I will venture more into finding some answers when I have a bit more free time. Medical school is a very jealous mistress. Regards,

Kyle

cardogab7341 · 2013-08-14, 17:33

I have a similar setup, an I7 3820 with an ASUS P9X79 PRO MB, and 16G of quad-channel RAM. I did overclock to 4.6G, and the system ran like this for 6 months, during which time it processed 4 exponents in the 52M-62M range every 12-14 days (18-22ms per iteration,depending on the exponent). It does run hot, I used this heatsink, and even with this monster the temps were in the 80-85deg. C range. I also had to increase Vcore to around 1.48V to keep the system from blue-screening once a month or so. So, you can overclock to get better performance, but your CPU will run HOT and it will consume about 140W (according to CoreTemp). I stopped running recently when the temps here in Texas started getting into the 100's (deg. F) because my office was getting too hot.

Mark Rose · 2013-09-15, 03:14

Quote:

Originally Posted by Primeinator

I possess an i7 3820 at 3.6 GHz; however, it appears to be automatically overclocking to 3.75 GHz without any action on my behalf. This I discovered from CoreTemp. For the purposes of LL testing, would I gain much benefit from overclocking further? Is this safe to do? Or is it better to keep it at its current level to avoid dramatically increasing the potential for error?

Other stats: 16GB DDR3 RAM at 2133 MHz.
High-performance cooling (temps pretty constant at 51-54)

Thanks!

If you are running mprime/Prime95, you are memory bandwidth bound at those frequencies. Increasing your CPU clock won't help much. Try increasing your memory frequency along with increasing the timings, e.g. 2133 MHz -> 2400 MHz, CL9 -> CL10.

TheMawn · 2013-09-15, 04:54

Quote:

Originally Posted by Mark Rose

If you are running mprime/Prime95, you are memory bandwidth bound at those frequencies. Increasing your CPU clock won't help much. Try increasing your memory frequency along with increasing the timings, e.g. 2133 MHz -> 2400 MHz, CL9 -> CL10.

He is very far from being memory bandwidth bound as he has access to quad-channel RAM which is twice as fast as dual channel. It's as though he is running 4266 MHz memory which is enough to cover probably 8 GHz on four cores if such a thing were possible.

chalsall · 2013-09-15, 08:00

Quote:

Originally Posted by TheMawn

He is very far from being memory bandwidth bound as he has access to quad-channel RAM which is twice as fast as dual channel. It's as though he is running 4266 MHz memory which is enough to cover probably 8 GHz on four cores if such a thing were possible.

Absolutely no disrespect intended, but please do not assume that just because (for example) the car manufacturer and/or sales person says it gets 100 mpg that it actually does.

It might... Or, then again, it might not... It can get really complicated really quickly....

2013-08-13, 18:22	#1
Primeinator "Kyle" Feb 2005 Somewhere near M52.. 3·5·61 Posts	Overclocking I possess an i7 3820 at 3.6 GHz; however, it appears to be automatically overclocking to 3.75 GHz without any action on my behalf. This I discovered from CoreTemp. For the purposes of LL testing, would I gain much benefit from overclocking further? Is this safe to do? Or is it better to keep it at its current level to avoid dramatically increasing the potential for error? Other stats: 16GB DDR3 RAM at 2133 MHz. High-performance cooling (temps pretty constant at 51-54) Thanks!

2013-08-13, 23:32	#6
kladner "Kieren" Jul 2011 In My Own Galaxy! 2·3·1,693 Posts	Bingo! (Although TheMawn did explain the whole thing very well, too.) Last fiddled with by kladner on 2013-08-13 at 23:34

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2013-08-13, 21:11	#2
lavalamp Oct 2007 Manchester, UK 2²×3×113 Posts	Sounds like the turbo is kicking in, that is the expected behaviour. It usually only does this when 1 or 2 cores are loaded and the others are idle. I think with this CPU you can up the multiplier all the way to 43 (to give you 43 * 100 = 4300 MHz), which should be stable with a moderate (read: small) increase in Vcore. However if you do that make sure you run Prime 95 torture test and Intel Burn Core for a while to make sure. Unfortunately, you cannot overclock your chip further as only the unlocked k models of Intel CPUs have such functionality. When overclocking you would see essentially a linear scaling of performance with clock speed in all applications that aren't limited by some other aspect such as memory bandwidth/capacity, but it sounds like you're doing fine there with 16 GB of 2133 Mhz RAM (I assume dual channel, but if quad channel then woohoo!). You CAN change the BCLK (base clock) to overclock further, but really really don't do that, it can cause all kinds of problems as that clock is used by all kinds of other chips on the motherboard and it can very easily cause your PC to become unstable. The Sandy Bridge chips are fairly easy to overclock, and there are lots of guides around to help with things like voltages. As long as you keep the temps under control (sub 80 or 90 C), you should be fine.

2013-08-13, 22:26	#3
Primeinator "Kyle" Feb 2005 Somewhere near M52.. 3×5×61 Posts	I am pretty sure it is dual channel. How do I confirm? A few quick Google checks do not help (much). My Computer ---> Properties only says 16 GB. Is there a way to tell?

2013-08-13, 23:16	#4
TheMawn May 2013 East. Always East. 6BF₁₆ Posts	Your chip may not be very overclockable. It wouldn't surprise me if your chip isn't unlocked. On the other hand, it is an expensive chip for an expensive lineup, so maybe you CAN get it to at least 4300MHz which is definitely worth it if your cooling can handle it. You will need more voltage, and both frequency and voltage will contribute to extra heat. The easiest way to tell if you're using dual or quad channel memory is to take off your computer's side panel and find the memory. It'll be near the top middle of your board. Check to see how many sticks you have and where they are. You should have four slots on either side of the CPU, and they should be two different colours. For example, you might have: black - blue - black - blue - CPU - black - blue - black - blue 16GB is most likely going to be 4x4GB, though it might be 2x8GB and very unlikely to be 8x2GB. If you have eight sticks, you're set and using quad channel. If you have four sticks, make sure that they are all in the same coloured slots. They should therefore NOT be all on the same side of the CPU. If you have two sticks, make sure that they are again in the same coloured slots. This is dual channel. The advantage of quad channel over dual channel is that your motherboard essentially sees the set of four sticks as ONE giant stick with four access points, and so quadrupled bandwidth. The "sets" are denoted by colours. This information should also be in your motherboard's manual if you have one. A less experienced computer builder might have been tempted to slide the RAM sticks in sequentially: black - blue - black - blue - CPU - DIMM - DIMM - DIMM - DIMM Instead of the correct: black - DIMM - black - DIMM - CPU - black -DIMM - black - DIMM

2013-08-13, 23:32	#5
kracker "Mr. Meeseeks" Jan 2012 California, USA 2³·271 Posts	Or another way to see if it really is on dual channel, just run CPU-Z and goto the Memory tab and it'll tell you a lot about your memory.

2013-08-14, 04:45	#7
Primeinator "Kyle" Feb 2005 Somewhere near M52.. 3·5·61 Posts	Thank you to everyone who posted. I appreciate both your willingness to answer my questions and your patience for my ignorance and lack of knowledge most of this forum perceives as highly rudimentary. I will venture more into finding some answers when I have a bit more free time. Medical school is a very jealous mistress. Regards, Kyle

2013-08-14, 17:33	#8
cardogab7341 Mar 2013 Dallas, TX 2×3×5 Posts	I have a similar setup, an I7 3820 with an ASUS P9X79 PRO MB, and 16G of quad-channel RAM. I did overclock to 4.6G, and the system ran like this for 6 months, during which time it processed 4 exponents in the 52M-62M range every 12-14 days (18-22ms per iteration,depending on the exponent). It does run hot, I used this heatsink, and even with this monster the temps were in the 80-85deg. C range. I also had to increase Vcore to around 1.48V to keep the system from blue-screening once a month or so. So, you can overclock to get better performance, but your CPU will run HOT and it will consume about 140W (according to CoreTemp). I stopped running recently when the temps here in Texas started getting into the 100's (deg. F) because my office was getting too hot.