Strange overclocking results (8700k)

[Erlijus]

Hey guys, looking for help there as I am a bit of a loss. 

 

Built my new rig around 8700k, ASUS ROG Z370-F, Corsair H100i v2, G.Skill Ripjaws V DDR4 3200 (2x8 GB). My goal is to achieve 5GHZ in turbo mode on all 6 cores, which seems to be very doable with that build. Yesterday, I thought I reached my goal, as I got no error in Prime95 after 1 hour of tests (blend, mix of everything): I set the 6 cores at 50 in BIOS, and Vcore manual at 1.35. Temperatures never went above 86 celsius (package, in HWmonitor). But then I noticed something strange: even if the XMP profile was enabled in BIOS, as I set "Allow odd DRAM timers" to disabled in BIOS, memory was not running at 1600 MHz but at its native speed, 1033 MHz...

 

So today I enabled this settings in the BIOS, and I can not reach anything stable: I always get error on the second test of the Prime95 blend tests (the 8k FFT one, producing lots of burst of rapid calculus on your CPU). Temperatures are much higher (around 90-92 celsius), and I always get the rounding errors. So I am kind of back to square one so far: it seems I can either run at 5GHz 6 cores but with RAM in JEDEC mode, or at the default of 4.3 GHz on all corers with RAM in XMP mode... I am hesitant to push the voltage higher, as I already reach 90-92 celsius...

 

Any idea? Does anyone have the same experience with the same mobo ? BTW I have the latest BIOS, 0430.

 

Thanks,

[gbergeron]

15 minutes ago, Erlijus said:

Hey guys, looking for help there as I am a bit of a loss. 

 

Built my new rig around 8700k, ASUS ROG Z370-F, Corsair H100i v2, G.Skill Ripjaws V DDR4 3200 (2x8 GB). My goal is to achieve 5GHZ in turbo mode on all 6 cores, which seems to be very doable with that build. Yesterday, I thought I reached my goal, as I got no error in Prime95 after 1 hour of tests (blend, mix of everything): I set the 6 cores at 50 in BIOS, and Vcore manual at 1.35. Temperatures never went above 86 celsius (package, in HWmonitor). But then I noticed something strange: even if the XMP profile was enabled in BIOS, as I set "Allow odd DRAM timers" to disabled in BIOS, memory was not running at 1600 MHz but at its native speed, 1033 MHz...

 

So today I enabled this settings in the BIOS, and I can not reach anything stable: I always get error on the second test of the Prime95 blend tests (the 8k FFT one, producing lots of burst of rapid calculus on your CPU). Temperatures are much higher (around 90-92 celsius), and I always get the rounding errors. So I am kind of back to square one so far: it seems I can either run at 5GHz 6 cores but with RAM in JEDEC mode, or at the default of 4.3 GHz on all corers with RAM in XMP mode... I am hesitant to push the voltage higher, as I already reach 90-92 celsius...

 

Any idea? Does anyone have the same experience with the same mobo ? BTW I have the latest BIOS, 0430.

 

Thanks,

It seems like the RAM oc'd create instability

 

Did you try to raise a bit VCCIO and SA voltage ?

 

I think it is better to run it at 5.0 ghz @ stock ram than 4.7 @ 3200 mhz

[AlexTheGreatish]

XMP does a really good job at making systems questionably stable.  Your best bet is to manually overclock the RAM too, although this will add a bit of heat.  What do you plan on doing?  Might be better off just setting 2 cores to 5 and then the rest to like 4.5 or something, it'll still smash games.

[Erlijus]

39 minutes ago, AlexTheGreatish said:

XMP does a really good job at making systems questionably stable.  Your best bet is to manually overclock the RAM too, although this will add a bit of heat.  What do you plan on doing?  Might be better off just setting 2 cores to 5 and then the rest to like 4.5 or something, it'll still smash games.

Interesting facts: by disabling XMP and manually configuring the same settings, and by using a Vcore offset of 0.02V instead of a manual Vcore of 1.35V, I can reach 4.7 GHZ stable on all 6 cores, with temp max for package being 92 celsius during the 8K FFT test (the most CPU intensive one). I will try to push a bit further. If I can not, I will settle to your recommendation: 2 or 3 cores at 5, the rest at 4.5 or so.

[AlexTheGreatish]

Do you know how much voltage it's getting under load?  Also what are you using the computer for?  For games that's fine but if you're rendering things I'd try and get the temps a bit lower.

[Erlijus]

10 hours ago, AlexTheGreatish said:

Do you know how much voltage it's getting under load?  Also what are you using the computer for?  For games that's fine but if you're rendering things I'd try and get the temps a bit lower.

Ok so an update this morning: I managed to run a stable 5.0 GHZ OC on all cores, but I am not satisfied with the results, at all. I seem to have gotten a really bad 8700K. Basically, to pass the Prime95 blend tests, I have to put an offset of 0.03V on Vcore and a Load Line Calibration of 4 (Auto or 1 to 7 on ASUS Boards). According to HWmonitor, the Vmax delivered to the CPU under load is 1.411V, which leads to a power of 185W and a temp max of 97 celsius. I even saw some cores of the CPU throttling down to 3700 MHz during the most intensive Prime95 (8K FFT).

 

I use the machine mainly for gaming and streaming, plus regular office work. Nonetheless, as a nerd/geek I like to push my machines to the limit... In short, I do not know what to do with this, as I read some posts of people with the same mobo/cpu who easily reach 5 GHz on all cores... There is even an option in ASUS UEFI to load presets for 5GHz stable (which obviously lead to unstability for me).