Anbody else 'underclock' their 9900k?

It seems to me that 5ghz on 2 cores is quite useless for me. The only thing I do which requires a fast CPU is gaming and even if a game uses 1 or 2 threads, other background processes will be constantly doing stuff meaning you'll basically always be running 4.7ghz.

So I decided to ditch 5ghz at this point and see what speed I can reach on all cores to improve game fps.

Currently I've got max boost multiplier to 49. Ditching 5ghz means I can use a lower vcore offset. The CPU never goes above 1.29v and droops down to 1.26 under full load. LLC level 3.

Of course I will see if I can hit 5 or 5.1 but I have a feeling that 4.9 is the sweet spot on this CPU.

Anybody else do a similar thing? What are your results?

 

I wonder how many gurus have this CPU...

 

I have mine at 5 Core / 4.7 Cache at 1.3v fixed voltage.

 

Sounds like a good chip. I'm certain mine wont manage 5ghz with 1.3v.

Why don't you run offset mode so that the cpu can power down when it's idle?

 

The idle temps are the same at fixed voltage and the lifespan of the CPU is not really affected. Still would like to lower the voltage at idle but need time to test it out.

I had tried adaptive mode but was not stable probably because the voltage regulator is not fast enough to switch from a low voltage to the highest voltage. When I went to run Cinebench, CPU went to 5GHz but the voltage stayed at 0.9V for like a second resulting in BSOD. Might be the same issue with offset mode. Plus there is adaptive+offset mode. I would like to understand better the difference between adaptive and offset modes.

On my previous i5 4690K, adaptive voltage worked fine with a 4.6GHz overclock but I had to disable c-states because the system would freeze when I was just browsing or the system was idle but never during load. C-states worked fine when not overclocked. On the other hand, c-states don't cause issues with the 9900K. These power saving features are nice but they might be tricky to get to work reliably with overclocking.

 

Hey, I am currently running my 9900K at 4.9 GHz all cores in adaptive mode.

1.307 V max on non-AVX loads
1.281 V max on AVX loads with -1 AVX offset (4.8 GHz all cores)
PL2 unlimited
IccMax unlimited
Speedshift enabled (Hardware P-states instead of using Speedstep)

With a Noctua NH-U12A heatpipe on an EVGA Z370 Classified K motherboard I have seen some cores up to 90°C whilst rendering h265 video.

The VRMs never break a sweat on this board, highest I have seen is ~60°C, even after hours of (overnight) rendering.

 

Adaptive was a disaster for me too. Regardless of what I do, the minimum turbo VID was 1.42V!

Adaptive is supposed to override the CPU's default turbo VID, only when multiplier(s) go above stock behaviour. So if you set 1.3 and change the multipliers, it should set a VID of 1.3V under load. As I said, it doesn't work at all for me.

Offset just adds your offset to the CPU's default VIDs.

Offset works really nicely for me. I set an offset of +.12v and turbo works nicely at the VID I need, VID and multiplier drops down when idle.

Does anybody know what the default max AVX and Cache speeds are? I'm wondering what I should set for those if I want to retain 'stock' speeds for those?

 

AVX offset is 0 by default, allowing 4.7 GHz on all cores.

Cache multiplier is 43 by default.

 

Thanks

 

What's the default VID for the 9900K? Or is it best to change back to stock, run a load and see the voltage and offset to that?

 

I think the VID varies from chip to chip and is set per 100mhz.

I would change to offset mode and put your OC back to stock 4.7 all cores. See what vcore you're getting in Windows and then adjust the offset to get back to whatever voltage you needed under load @ 5ghz.

 

4.7 on all cores is not actually stock. That's with MCE/Enhanced Turbo enabled. So this is what I tried. Checked the vcore at stock with Intel Turbo enabled (MCE disabled) and it was running at 1.312v vcore and maximum 1.333v VID from all cores on load.

Tried with the 5GHz overclock on. Set offset mode and left it on auto. Ran OCCT and the vcore was staying at 1.312v. So I inputted a negative offset of 0.01v to get to a ~ 1.304v vcore just like in fixed mode (I have LLC mode set to 3). Ran a quick OCCT 10min test. No errors detected. Closed it and went to open something else. Bam! System freeze. Not during stress test just normal desktop usage.

Tried with a lower negative offset (0.05). Was checking out CPU-z ( no stress test) and got a system freeze and after some seconds a BSOD.

Tried to leave it on Auto offset. Got a system freeze for a couple of seconds but recovered. Got another one and it recovered again. So yeah, back to override mode for me. Never had a system freeze with override mode. It could be the c-states or it could be that I have the second monitor connected to the Intel iGPU which maybe it is affecting the stability. I have not overclocked or messed with the voltages of the iGPU.

I still don't know what offset mode is actually offsetting though. Is it the maximum VID out of all cores or the maximum vcore? Or does it offset the VID/Vcore at each different multiplier? Still think that the voltage regulator is the culprit for not being fast enough to change between voltages when load changes.

 

Incorrect.

Have a look at the "Per Core Turbo Ratios".

Running MCE results in all cores running at 5GHz.

 

I meant 4.7 is the stock speed when all cores are loaded so you'll see what the max stock VID/vcore that is supplied to your CPU by default.

Yes it applies an offset to the stock VID requested by the CPU at each multiplier/turbo state.

Yes, it does sound like something like that.

 

Ok I think I found the right config for dynamic voltage without issues.

So first I tried again with offset mode in negative but this time tried to disable/enable CPU power save features. Disabled c-states, enabled C1E (by default disabled), disabled EIST with Speed Shift enabled, enabled EIST with Speed shift disabled. Nothing worked. Guaranteed system freeze without BSOD within 3 minutes of restarting while idling.

Then tried again with Adaptive voltage mode. Started with 1.3v vcore. While stress testing it went up to 1.36v. Tried 1.25v but still goes up to 1.34v and then with 1.2v going up to 1.32v. Surely there must be a better way to do this.

So I decided to try that Adaptive + Offset voltage mode that nobody seems to ever mention let alone use. I started again with 1.3v adaptive vcore with a negative offset of 0.06v (1.36-1.3). During stress testing vcore went up to 1.296v. Not enough for stability. Reduced negative offset to 0.05v and now goes up to the 1.304v that I need.

But it's not when the system is under full load that is the issue but during normal usage. So I have been using the PC like normal and leaving it idle and so far no system freezes. Voltages and frequency changing like in stock. C-states are set to auto and both EIST and Speed Shift are enabled. Hopefully it stays like this.

 

Nice one. I've had similar issues, getting it stable under a full-load like Cinebench extreme is easy. Finding stability during gaming or light use can be a PIA.

Now I've got a (hopefully) stable system using offset, I might try adaptive with a -ve offset. The only issue with offset is that idle/light use voltages are a bit higher than necessary - not really a big deal but I like punishing myself, so I'll give it a go!

 

Well I tried adaptive again, it's a no-go. It's a total basket-case on my motherboard. It gives way too much voltage and still manages to be unstable. I'll stick with offset.

 

Did you try adaptive + offset mode?

 

Yes, I think adaptive is fundamentally broken on this board/BIOS. It gives way too much voltage at full load and not enough at lower p-states. Adding a -ve offset just makes that latter worse.

Offset works nicely, it runs well at 4.9, never going over 1.29V with a very low LLC. I tried 5ghz which seemed stable at 1.31v but added 10C so I'll leave it at 4.9ghz.

 

it gets mighty toasty on my watercooling at 5Ghz, so i settled with a clock of 4.7. maybe if i get some games that really need more cpu i'll stick it at 4.9Ghz but until then i'm happy with 4.7Ghz.