Hello Tom's Hardware members.
I am having quite a time overclocking my retro/modern gaming PC's CPU (which is also my main PC, 'cause it is the most powerful PC I own), and I was wondering if you could help me out.
As courtesy, here's a quick list of it's specs:
Okay, so recently I upgraded the i5-750 in the system to an i7-870, and so, wanting to squeeze a bit more juice out of the system, I decided to overclock it to 3.6GHz, the "max" turbo frequency of the CPU, as stated on Intel's website. However, if I remember correctly, I noticed some strange things happening in Prime95. I decided then to bump down to 3.2GHz, the highest speed that I have ever seen this CPU turbo up to on default BIOS settings. Again, the same result. And today, just now, I decided to turn off load-line calibration to see what would happen, and again, although better this time, the same thing happens.
What I am talking about are "random" drops in CPU usage while running Prime95 using the "Small FFTs" torture test. The torture test chugs along just fine, when all of a sudden you can see in Task Manager CPU utilization drop from 100% to ~40% for like 3-5 seconds, then going back up to 100%. The higher the overclock, and (it seems) the more voltage that is being feed to the CPU, the sooner this event happens and the quicker it happens again in the torture test.
Now, let me preface by saying I am a completely new novice at CPU overclocking (the only other overclocking experience I have is in overclocking a Voodoo3 3000 in my Pentium 3 machine, and that's it). My current settings in the BIOS are to enable "XMP" in "High Frequency" mode, so that the custom timings for the RAM are given to the motherboard, then with the multiplier set to 24, BCLK to 133, QPI the lowest frequency available, all voltages set to auto (except RAM, with the XMP profile setting it to 1.65V), and all power settings (such as C-state stuff) disabled. It seems that any overclock up to 3.6GHz is stable, from what I can tell, but that Prime95 somehow brings the system down in such a way as to reduce CPU usage during the torture test to half of what it should be.
Now, from what I have read, these events point to poor VRM cooling, bad VRMs (at least quality-wise), or (and this is me guessing) just not "strong" and "robust" enough of a VRM solution. I did notice that, after replacing the dusty old thermal pad with new cheap Chinese ones, and then replacing those with Arctic's thermal pads, which are 4x more thermally conductive at 6.0W/mK, that the time between me starting Prime95's torture test and the first occurrence of CPU usage dropping increased, so this has me to believe that the motherboard's VRMs are somewhat responsible for this "instability".
So, what I want to know is this: Is it indeed a VRM problem, some other problem or combination of problems entirely, or something that really means nothing? I doubt it means nothing, because I can't ignore the feeling that something's not right.
Any help would be appreciated. Thanks!
I am having quite a time overclocking my retro/modern gaming PC's CPU (which is also my main PC, 'cause it is the most powerful PC I own), and I was wondering if you could help me out.
As courtesy, here's a quick list of it's specs:
■ Intel Core i7-870, cooled by an Artic Freezer 33 eSports edition cooler (the one with two fans on it)
■ Asus P7H55-M Micro ATX motherboard
■ 8 GB G.Skills Sniper 2133MHz DDR3 RAM
■ EVGA Nvidia GeForce GTX 780 Ti
■ Sound Blaster X-Fi PCIe soundcard
■ Corsair TX650M 650W 80+ Gold PSU
■ Windows 10 Pro
Okay, so recently I upgraded the i5-750 in the system to an i7-870, and so, wanting to squeeze a bit more juice out of the system, I decided to overclock it to 3.6GHz, the "max" turbo frequency of the CPU, as stated on Intel's website. However, if I remember correctly, I noticed some strange things happening in Prime95. I decided then to bump down to 3.2GHz, the highest speed that I have ever seen this CPU turbo up to on default BIOS settings. Again, the same result. And today, just now, I decided to turn off load-line calibration to see what would happen, and again, although better this time, the same thing happens.
What I am talking about are "random" drops in CPU usage while running Prime95 using the "Small FFTs" torture test. The torture test chugs along just fine, when all of a sudden you can see in Task Manager CPU utilization drop from 100% to ~40% for like 3-5 seconds, then going back up to 100%. The higher the overclock, and (it seems) the more voltage that is being feed to the CPU, the sooner this event happens and the quicker it happens again in the torture test.
Now, let me preface by saying I am a completely new novice at CPU overclocking (the only other overclocking experience I have is in overclocking a Voodoo3 3000 in my Pentium 3 machine, and that's it). My current settings in the BIOS are to enable "XMP" in "High Frequency" mode, so that the custom timings for the RAM are given to the motherboard, then with the multiplier set to 24, BCLK to 133, QPI the lowest frequency available, all voltages set to auto (except RAM, with the XMP profile setting it to 1.65V), and all power settings (such as C-state stuff) disabled. It seems that any overclock up to 3.6GHz is stable, from what I can tell, but that Prime95 somehow brings the system down in such a way as to reduce CPU usage during the torture test to half of what it should be.
Now, from what I have read, these events point to poor VRM cooling, bad VRMs (at least quality-wise), or (and this is me guessing) just not "strong" and "robust" enough of a VRM solution. I did notice that, after replacing the dusty old thermal pad with new cheap Chinese ones, and then replacing those with Arctic's thermal pads, which are 4x more thermally conductive at 6.0W/mK, that the time between me starting Prime95's torture test and the first occurrence of CPU usage dropping increased, so this has me to believe that the motherboard's VRMs are somewhat responsible for this "instability".
So, what I want to know is this: Is it indeed a VRM problem, some other problem or combination of problems entirely, or something that really means nothing? I doubt it means nothing, because I can't ignore the feeling that something's not right.
Any help would be appreciated. Thanks!