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Discussion Starter #1
Hello folks,

I bought a 9900KF recently because of the price cuts and already having a Z370 board - an Asrock Extreme4 - with good enough VRMs to handle it (at least according to Google). Getting it to 5GHz stable at a relatively low fixed voltage is proving to be a hassle, but I don't think it's because the chip itself is garbage tier.

If I set a fixed voltage of 1.32V, which HWiNFO reports as 1.312V, I can run OCCT and Aida64 tests indefinitely at 5GHz but I'm lucky if it lasts more than three seconds in the P95 Small FFT without AVX. I went all the way to 1.39V fixed and Small FFTs were still hard crashing immediately. I have LLC on level 1 (Asrock's highest) and have disabled all of the power saving features - SpeedStep, SpeedShift, C1E, etc. VCCIO and VCCSA are 1.1 and 1.15 respectively; increasing both to 1.3 makes no difference.

With all settings reset to default, except for setting the core ratio to 50 and loading the XMP profile, the CPU has stupid voltages at idle - about 1.45V - but drops to 1.312V in the Small FFT test and is stable. The temperatures are high 70s/low 80s so I'm guessing that voltage reading is more or less accurate.

Am I missing something obvious? I do have a stable 4.9Ghz config but that needs a fixed BIOS voltage of 1.35V (reported as 1.328V), which seems high for this chip.

Any help appreciated.
 

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That's a very high LLC and can be part of the problem. Try dropping LLC to your 2nd or 3rd setting, and compensate for the vDroop by adding a little more BIOS voltage. I'm not saying this is for sure the issue, but with an LLC that high, you could very well be spiking the chip with 1.5v when you start a heavy load like P95, causing the chip to freak out and fail. Transient voltage spikes can be unseeable with software, and with an LLC that high, you are for sure going to be slamming the chip with massive spikes.

Try LLC3, and adjust your voltages after you see what that gives you under load.
 

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Z370, although it can technically run 9th gen CPUs does not seem to handle them very well under overclock.
They want higher than normal voltage for the CPU to be stable.
It's not just the VRM quality, it is more the VRM design in general.
I was running a 9700K on a Gigabyte Z370 Aorus Gaming 7 that had the best VRM for the Z370 series and could not get past 5.0GHz @ 1.35v. 5.1 required close to 1.4 spiking over that with LLC set to Turbo.
Always seemed weird to tweak compared to my 8700K which it replaced.
Put the 9700K into a Z390 board (Asus Prime Z390-A), and it does 5.0GHz @ 1.30v, 5.1 @ 1.325 with less voltage spike from LLC.
VRM temps much cooler also.

Honestly, I wouldn't go higher than a 9700K on a Z370 board. 9900K just draws too much power when overclocked.
Stock, OK on a good Z370 board.
 

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Discussion Starter #4
Thanks both. I changed to LLC3 and, while 5GHz is still freezing instantly on Small FFTs whatever the fixed voltage, the actual voltage during the same test at 4.9GHz is 1.264V (although only tested for 20 minutes so far). I think you're right @jonkrmr about the limitations of the Z370 - the CPU seems perfectly capable if it can do 4.9GHz at that voltage but I would really have to brute force it for the next 100MHz. Even if that worked, it wouldn't be worth the thermals/noise.
 

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Z370, although it can technically run 9th gen CPUs does not seem to handle them very well under overclock.
They want higher than normal voltage for the CPU to be stable.
It's not just the VRM quality, it is more the VRM design in general.
I was running a 9700K on a Gigabyte Z370 Aorus Gaming 7 that had the best VRM for the Z370 series and could not get past 5.0GHz @ 1.35v. 5.1 required close to 1.4 spiking over that with LLC set to Turbo.
Always seemed weird to tweak compared to my 8700K which it replaced.
Put the 9700K into a Z390 board (Asus Prime Z390-A), and it does 5.0GHz @ 1.30v, 5.1 @ 1.325 with less voltage spike from LLC.
VRM temps much cooler also.

Honestly, I wouldn't go higher than a 9700K on a Z370 board. 9900K just draws too much power when overclocked.
Stock, OK on a good Z370 board.
Gigabyte motherboards are known to require more vcore to achieve the same clocks compared to Asus.
 

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That's not the point of the conversation. Z370 was designed for a 6c\12t processor. VRM and power delivery was designed to meet Intel spec for 6c\12t 8th gen processor.
Power delivery and requirements changed with 9th gen and although Z370 can power 9th gen processors, they are not optimized for them.

They can run them fine at stock speed but depending on the quality of the board\VRM and power delivery design used........

9900K - 8c\16t is a beast and pulls a lot of power under load especially when overclocked and better suited to a Z390 board with a VRM\power delivery designed for the load.

I am curious to know what the VRM temp is under load with a 9900KF and Asrock Extreme 4 Z370 board with the CPU at 5GHz 1.35+ v.

I had to water cool my VRM on my Z370 board with a mono block to keep the VRM temp in check.

The Gigabyte Z370 Aorus Gaming 7 used Intersil top of the line (for the day) 60A phases. 4 phases to CPU that are doubled. 480A power capability to the CPU. Only problem with the board was the crappy VRM heat sink they used.
 

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VRM Load-Line Visualized - ElmorLabs
2478954

With a high LLC level, you get the massive voltage drop prior to load and spike afterward. The drop (circled in red) can cause crashes, as the voltage may be insufficient for the load. The spike in orange shouldn't cause crashes, but may harm the CPU over time.

Fyi, I have an EVGA Z370 Micro that is more than capable of handling a 9900K at 5.2GHz. As Buildzoid pointed out, it had the best VRM among the z370 mATX class and very capable finned heatsinks.
 

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Discussion Starter #8
I am curious to know what the VRM temp is under load with a 9900KF and Asrock Extreme 4 Z370 board with the CPU at 5GHz 1.35+ v
I've settled for 4.9GHz at 1.32V/LLC3 and the highest VR VCC temp I've seen so far under stress testing is about 75c, so it seems to be handling itself fine.

These settings are actually working quite well - my NH-D15 (in a mesh case) can keep the temps in non-AVX testing to about 55-60c, so the fans don't spin up even under load. It'd be nice to get 5GHz with the same thermals/noise just because 5 is a bigger number but I can wait until whenever a successor CPU offers some significantly better for that.
 

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I figured your VRM temp would be at the upper range of usable.

Kind of the same thing I ran into overclocking a 9700k on my old Z370 Aorus Gaming 7, could not get all the potential I could get from the CPU.
I put the CPU into a Z390 board and it was much easier. Able to get higher overclock with less voltage and heat.
 
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