XMP causes extreme CPU overheat

[Rookie92]

Hi all, I just finished my first PC build the other day, but i'm having trouble with the XMP on my Trident F3-12800CL8D-4GBTD Memory. I'm running it with an Intel Core i5 750 on a Gigabyte p55a-ud3.

The board and the memory both support X.M.P but when i enable it in the BIOS it causes my CPU to massively overheat, with x.m.p. on, it idles around 50 c and within 2 minutes of being put under full load it will hit high 80's and soon into 90's. I thought i maybe didnt install the cooler properly (its not aftermarket and i stuck with the thermal grease that is initially on the base of the heatsink) but when i checked it was definitely on as it should be. I then tried turning my X.M.P off and my temperatures went to were they should be, 38ish at idle and 68ish at full load. Im just wondering why this is, i have done no manual oc'ing (just swithching my x.m.p on and off) and with x.m.p on the memory was running at its advertised speeds and timings, at 1.6 volts (as opposed to 1.5 without x.m.p). Anyone else noticed anythig similar? Have a solution? I would appreciate anyones help with this! Also note i live in ireland and it is late here so i may not be back on the forum for several hours!

[GSKILL TECH]

Manually set the QPI/VTT Voltage to 1.25V and see if that helps.

Thank you
GSKILL TECH

[Rookie92]

Thanks for the response, i tried it but temps still got way too high, 60 at idle and i only ran prime95 for a few seconds before stopping it as temps hit 90. So i turned XMP back off and lowered Vtt Voltage back to 1.1. Thanks again

[Sin]

You have the latest BIOS for that motherboard? Where are you checking you CPU temperature?

[Rookie92]

Yes i believe i do have the latest BIOS, I tried using gigabytes updater which said none were available, I have checked the temps in realtemp, open hardware monitor and in my BIOS aswell and readings from all of them match up.

[Sin]

You have 2 sticks of memory? Did you try to run with XMP and only one stick?

[Rookie92]

No i haven't tried that, I didn't think that would make a difference because the XMP changes the BCLK and the multiplier, regardless of the amount of memory actually in the mobo. I figured this increase in BCLK is the cause of the overheat, even though the total increase in Mhz is only 60 (XMP on: 160 BCLK x17 multiplier = 2720 mhz; XMP off: 133 BCLK x20 multiplier = 2660 mhz.) Do you think it would be different with just one stick of ram? Thanks

[Sin]

Oh, just found a clue when you posted BCLK at 160 MHz with XMP on. If you have your CPU voltage set to AUTO in BIOS with XMP on, compare it to the CPU voltage with XMP off, looks like motherboard increase CPU voltage a lot if you leave it at AUTO. Try to adjust that voltage, if you have it around 1.14 V without XMP then set it to 1.15-1.16 with XMP and check your temperature. You might need even a little higher CPU voltage if system becomes unstable. BCLK is with XMP a little bit overclocked (160 vs default 133) and some motherboards just push too high voltage to CPU as a safe measure. Give it a try and check it...

[Rookie92]

Thanks i'll be sure to try that soon and let you know how it works. Is the CPU voltage the one labelled Vcore in Bios? What is QPI/Vtt Voltage do you know?

[Rookie92]

Hmm i noticed strange things. Firstly i seem to have 2 "Vcore" Values, and i dont know what they are for. One is "CPU Vcore" and actually goes down from 1.1375 to 1.03125 when XMP is enabled, the other is just "Vcore" and goes up from 1.088 to 1.248 when XMP is enabled, but i cant seem to adjust that. It's all very strange, I took pictures of these Voltage values and posted them below so ppl can see and maybe offer advice, both pictures are my BIOS valuse with XMP enabled.

This one shows the un-adjustable V-core in my "Motherboard Intelligent Tweaker" main menu
http://img706.imageshack.us/i/image0083u.jpg/


This one shows my adjustable "CPU Vcore" in Voltage settings
http://img823.imageshack.us/i/image0084.jpg/

[Sin]

As I can see, QPI can be memory controller voltage, it should be 1.1 V at normal state.
Vcore on the first picture is over 1.2 V and that is a couse why can CPU become so hot. On my Asus P7H57D-V EVO it is maxed at 1.18 V, mainly below 1.14 V, drops down to 0.88 V at speedstep slowdown. Try to fix Vcore at 1.15 V. If you can't adjust it, try to press F1 when you are in BIOS, that unlocks some features in Gigabyte BIOS.

[Rookie92]

Thanks Sin im slowly but surely making progress with this! So i couldnt manage to change my Vcore so i figured it must be a problem with my CPU Vcore, i have a feeling the "Vcore" one may just be a reading of Volts somehow derived from "CPU Vcore". I couldn't understand why turning on XMP and slightly oc'ing my cpu would cause a decrease in the CPU Vcore like it did, so i turened CPU Vcore off auto and set it to its voltage without XMP (1.1375) When i did this and turned XMP on the Vcore that i couldnt change remained at 1.12 (previously it would go to 1.248 with XMP on) and the temps went down, they were around 80 at full load and 50 at idle! which is a huge difference but not quite enough. Im wondering if you could help me build on this development to get it to run cooler again? I'm confused because temps went DOWN by increasing my CPU Vcore but thats backwards isnt it? So i dont know if i should increase again or decrease slightly for cooler system. Help would be great! Thanks

[GSKILL TECH]

VCore is the current voltage reading in BIOS. CPU VCore is just what you set it at, but it may not operate exactly at this.

Sin is right, check CPU Ratio with XMP. On AUTO, it may keep CPU Ratio at max, but because of the BCLK increase it will also raise CPU Frequency, thus shooting CPU temps that high. The i5 750 CPU only has a 10X memory multiplier, which is why BCLK must be increased for DDR3-1600. If you had the i7 860 with 12X memory multi, it is able to retain BCLK 133. So manually set CPU Ratio 18X (2.880GHz) and temps should be fine.

QPI/VTT Voltage is good for 1.30V on stock CPU cooler, so that is not the problem.

Thank you
GSKILL TECH

[Rookie92]

O.K. I've had lengthy discussions on another forum so im just going to copy and paste excerpts from that to explain all the diagnostics i've done and perhaps you can help me out 'cuz i've given up myself! Thanks for the reply btw

When XMP increases the bclk to 160, it decreases the multiplier from x20 to x 17 (i checked the effects of XMP in BIOS), which results in a clock speed of 2720 (if my basic understanding of oc'ing is correct), but this is only a total increase of 60mhz compared to a 133 bclk with 20x multiplier, could this really cause such a drastic temp rise? Especially considering the processor is supposed to support turbo boost up to 3.2 ghz!

I seem to have 2 "Vcore" Values, and i dont know what they are for. One is "CPU Vcore" and actually goes down from 1.1375 to 1.03125 when XMP is enabled, the other is just "Vcore" and goes up from 1.088 to 1.248 when XMP is enabled, but i cant seem to adjust that. It's all very strange, I took pictures of these Voltage values and posted them below so ppl can see and maybe offer advice, both pictures are my BIOS valuse with XMP enabled.

This one shows the un-adjustable V-core in my "Motherboard Intelligent Tweaker" main menu
http://img706.imageshack.us/i/image0083u.jpg/


This one shows my adjustable "CPU Vcore" in Voltage settings
http://img823.imageshack.us/i/image0084.jpg/

I couldnt manage to change my Vcore so i figured it must be a problem with my CPU Vcore, i have a feeling the "Vcore" one may just be a reading of Volts somehow derived from "CPU Vcore". I couldn't understand why turning on XMP and slightly oc'ing my cpu would cause a decrease in the CPU Vcore like it did, so i turned CPU Vcore off auto and set it to its voltage without XMP (1.1375) When i did this and turned XMP on the Vcore that i couldnt change remained at 1.12 (previously it would go to 1.248 with XMP on) and the temps went down, they were around 80 at full load and 50 at idle! Which is a huge difference but not quite enough. Im wondering if you could help me build on this development to get it to run cooler again?
I'm confused because temps went DOWN by increasing my CPU Vcore but thats backwards isnt it? So i dont know if i should increase again or decrease slightly for cooler system. Help would be great! Thanks P.S. Vtt has been left at 1.1 throughout

[Sin]

Seems that you still have a problem with high voltage and overheating. With CPU voltage fixed at 1.1 there is no power saving on CPU. Check if Intel Speedstep and C1E support are enabled. Sorry that I can't give you more info on that, I have Asus motherboard and different settings in BIOS.
What kind of chasis do you have, medium-tower, without aditional cooler? Still Intel box cooler on CPU? If so, that can be a main reason why your temeperature goes so high. Buy better cooler, box cooler is OK if you have any better chasis with aditional coolers on it. But low quality chasis and box cooler make hot air to circle around CPU and you will have high temperature.