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Oc'ing i5 750 problems

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May 31, 2010 5:50:26 AM

I hope there aren't any previous threads to what is probably a simple mistake of mine in all of this >_>

I've had my i5 for a while and decided to see if I could push it a little bit (first time overclocking). I upped the bclk from 133 to 160, multi 20x, 3.20ghz easily the first time but it ran a bit hot. Reverted to stock settings, shut down, and left for a while.

I came back and set it to bclk to 150, same multi, to 3.00ghz. It's still fine. But I know that people easily pushed it to 3.4 on stock voltages so I decided to send it back up to 160 and this time remembered to disable turbo boost, eist, c1e, lower the QPI, etc. This time it won't even boot.

I checked the stock voltages and thought they were a bit high, vcore 1.2675v I think. But I went hunting around and other people have overclock's to 3.40ghz, same multiplier, bclk 170 with the same or an even lower vcore.

I tried someone else's settings as this

multi 20x
bclk 160
adjusted ram speed
vcore= 1.26875v
vtt= 1.210v
PCH=1.050v
PLL= 1.80v


Still a no go, it doesn't boot and the same message comes up saying it won't because of overclocking and changes in voltage. Setting a base clock of 150 is still fine with no other changes but I'd still like to try and hit 160. Oh, and my cooler is fine, it's an Arctic Cooling Freezer Pro rev. 2. It gets the temps down a little better than the stock. I just can't understand how it's saying the voltages aren't working!

Thanks for any replies

More about : ing 750 problems

May 31, 2010 5:58:19 AM

To be honest, I understand the physics of voltage (not that it helps too much with this lol) and that upping voltage can damage the cpu but that you do need to raise it to provide juice for some higher oc's. I was interested in not really altering the vcore too too much to get a stable overclock but if here's something odd with my stock voltages or if this requires a minor adjustment, I don't mind
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May 31, 2010 1:46:50 PM

Probably it's a RAM issue. When you overclock the baseclock the RAM also gets a frequency increase so you'll have to adjust them as well, either lower the RAM multiplier or try increasing the RAM latency. You should check out your RAM's timings in CPUZ or Everest and use those.
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May 31, 2010 5:02:31 PM

wow, thanks! I have 2x2 gigs of G.Skill DDR3 1600 pc12800 ram and it would boot when the bios auto-scaled the memory speed to 1500mhz. For some reason it would cop out at 1600mhz, but when I did the same multi, bclk, etc. except scaled back the memory ratio to 8:10 instead of 1:1, it worked! I have a Gigabyte P55 UD3R motherboard and for some reason the bios won't let you manually input a memory multiplier so it's stuck at 1280mhz but that's alright by me.

Stupid question then, DDR3 1600 PC12800 ram is rated up to 1600mhz? And if it is, was it the ram timings that I screwed up? I never went into checking those on the bios.

It seems to be working now, idle speeds at 40-41 c and I'm going to stress test it w/ linx and prime95 in a little bit.

Btw, can I enable eist and c1e after going through the testing? I don't really see a point in having it running full overclock all the time, specially since I don't want to waste electricity.
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May 31, 2010 7:48:55 PM

It depends on the RAM. Really good RAM might run 1600mhz at CL7. Mine's CL8, slower are CL9... if check CPU-Z it'll show you the JEDEC specs which are a universal rating, and then it'll probably show XMP settings for 1600mhz and all the related timings.

About RAM multipliers, they're usually locked to a few options. On the MSI and ASUS boards I've used the options are 10x, 8x, 6x. I OCed my CPU to 175bclk so initially my RAM I had at 1750 CL9, but then I read in Everest that my RAM is rated for 1400mhz CL7 so I put it at 175 x 8 = 1400mhz and CL7, and it's running great. CPU-Z only shows 1 or 2 XMP profile settings but in Everest there's a lot more info. Mine shows 3 different speed and timing options for XMP 1 and 3 more (same speeds, lower timings, higher voltage) for XMP 2. However, XMP 1 is certified (called "Enthusiast" setting) while XMP 2 is not certified (called "Extreme" setting). Mine do not run at XMP 2 speeds. For example it says 1600mhz CL7 1.7V but I couldn't even get it to boot at that speed without 1.75V at which point I said "ok eff this" and went back to 1.65V CL8 (fyi 1.65V is absolute max Intel spec for DIMM voltage).

EDIT: about your C1E and EIST question. You don't usually need to disable them unless going for an extreme OC. Depends on CPU but the i5 750 I have was able to do up to 170x20 with C1E, EIST, Turbo, C States all enabled and voltages at auto. I had to boost Vcore a little for 175 bclk but pretty much everything else is the same (well, I changed C States to C3 because of an ASUS board issue not for OC stability). If you're trying to hit 4ghz on all cores then you'll have to disable turbo and possibly C states. EIST is generally pretty save to have on and C1E I don't really know but I've never disabled it... I'd say try keeping them on since you like the energy savings and test it. If it fails up the vcore a bit you might have to up Vtt... if you're having some issues post all your settings full system specs and voltages and timings and maybe we can help you with some good advice.
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May 31, 2010 9:37:21 PM

I just thought it was something weird with my gigabyte board, maybe only higher quality boards can have manual memory multi's input cause I saw someone say they did it with their ram.

Haha I went through the same thing. I looked up the ram timings and turns out mine is CL7 and such and oughta run at 1600mhz. So I bumped up the ram voltage from 1.5v to 1.65. Still didn't boot and I was thinking "yeahh....1280 to 1600 mhz isn't that big a deal. whatever, i hit 3.20, that's good enough for me" lol. Yeah, under CPU-Z it shows the XMP 1 profile with the same ram timings that I put in and a lower voltage (1.60v) so that mystery will have to wait for another day.

Yeah, my bio prof is going through a bunch of ecology stuff now so I feel kind of guilty burning through all this power. Uhh, in that case I'll probably re-enable EIST and the C states but leave turbo off. I have an arctic cooling heatsink and it's better than stock but not incredibly great and I probably don't need turbo anyway. Once it finishes linx I'll reset that stuff then run it through prime95 for 3 or 4 hours. My stock vcore is already a bit high and you said you had no problem getting up to 170x20 on stock so it'll probably be fine (160x20) but I'll tweak vcore and/or vtt a bit if it messes up.
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May 31, 2010 10:06:22 PM

About voltages, I had to tweak them on my MSI board (I no longer have it) but my ASUS board does a good job of automatically adjusting. I'm not sure how Gigabyte is you may or may not have to bump them up.

I thought you said you couldn't change the base clock, but if it's the multi you're talking about then you should generally be able to do 9-20 but to get 21 you have to have EIST on auto. Also with 21x it will automatically turbo your CPU if you enable C States as well, but with C States off it'll just be a straight 21x. You should be ok at 160x20 with turbo. I'm just going to assume you play games, and most games only use maybe 2 cores sometimes 3 so turbo boost can be a nice help there as you'll get another 640mhz at 160 bclk.

I hope you've checked the Intel spec sheet but the short version is that their absolute max vcore is 1.55V and abs max vtt is 1.21V. I'm running right now at 1.21V Vtt at 175 bclk (Vtt is for the IMC or Integrated Memory Controller - basically the northbridge) Vcore needed is more dependant on your clock speed. For no turbo you can save on vcore but to reach that higher frequency it takes a bit extra voltage. For example I had my PC load up ok and then suddenly crash trying to do a 1 core operation, raising vcore solved it. Also Vcore adds to heat the most compared to Vtt.
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May 31, 2010 11:43:37 PM

Huh, I completely forgot about that. Yeah, I have been changing the base clock to overclock but haven't touched the multiplier, I don't think I'll have to. Now that you mention it though, I probably won't enable turbo. I guess it would be nice to have the speed boost but if it boosts too high, it might die like yours did because of not enough voltage.

Ehh, I mostly play shooters and the valve games I like usually have multi-core support. And I think Crysis 2 will have it too when it comes out :D DDD. They'll probably be ok without turbo; I think they'd benefit a bit more from getting a gtx 470 to replace my 8800gt lol. Hopefully I'll have the money for that

Oh, sorry about the miscommunication. When I said my stock vcore was a bit high, I meant that it's around 1.265 ish when I've seen lots of other ppl have theirs at 1.23 and achieve the same clock speeds. Vtt is probably ok as well but i'll double check that 1.21v number in my bios. Thanks for explaining vtt too, I didn't get it before. Heat is an issue for me though so I'll try to not touch voltages too much. The arctic cooling Heatsink i have is decent but not great quality, so it might not be able to handle the extra heat


I reset the power savers and made sure my vcore and vtt weren't too high. It's stress testing now, passed OCCT, currently running through 4 hrs of Prime95 at 76ish celsius then gonna run it through a bit of Linx. Hopefully all goes well, thanks!
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June 1, 2010 4:19:30 AM

Best answer selected by deltalives.
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June 1, 2010 4:35:30 AM

edit: never mind, read up on the 5c difference between Tcase and Tjunction and I think I'm ok. Probably should have gone for a better cooler but oh well, I won't push it that hard most of the time.

I'm guessing so long as Tjunction/Core temperature is within 5 degrees of Tcase (Intel says max Tcase for the i5 750 is 72.7c), then I'm ok (running 76ish c during testing)
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