9900KS...

[Oblivion]

Tell me about it! I've managed to get the cooler, two 140mm fans, and 4x 120mm case fans in there too! All on PWM so very quiet on idle.

Thanks, I'll give it a go

Cool! See how you get on! Bare in mind people quoting super low voltages are using high LLC! So you need to see what voltage under load is required to be stable and then how you achieve that is open to various overclocking methods and options etc. There are lots of guides out there, from people like MSI and Gigabyte etc if you google how to hit '5Ghz on an i9 9900K' (I know you have a KS but they are the same chip, but because yours in binned it should do lower voltages).

 

[PMKeates]

Well, I've been running some experiments yesterday. In short, I think if I want to run my 9900KS at 5.0 GHz or better all-core fixed, I need better cooling.

If I leave everything on default, including default Turbo periods etc., everything is fine - the CPU will ramp up, respecting the defined power and current limits and times. If I set an all-core permanent 4.8GHz, I can do this on 1.18v and it's 80c on long loads. If I set 4.9 GHz, I can do this on 1.24v and it's getting up to 90c in long loads (e.g. Asus Real Bench on loop), but reasonable and stable. If I try to set 5.0GHz permanent, after a small amount of extra voltage I'm hitting 100c thermal throttling and getting instability. To get a working system I need to go up to 1.39v and it causes so much thermal throttling it's pulling back to sub 4.5GHz to stay running, so in the end more efficient to just run at 4.9GHz/1.24v.

I suspect if I could keep temperatures under control at 5GHz, it would be stable - it's not possible in my view that a stable 4.9GHz at 1.24v requires 1.39v for 5GHz. I suspect 1.29v-1.3v would see a stable 5GHz, I just can't stop temperatures creeping up to 95-100c at e.g. 1.29v and the problems that brings with it.

 

[Oblivion]

Interesting analysis mate, i think you are hitting the limits of air cooling. You seem to have a good chip voltage wise, as to be expected with a KS.

I found this review to be the most relistic regarding temps and cooling a KS, see the graphs half way down the page, they basically said a custom loop or AIO is needed. Your findings seem to matched exactly.

https://www.tomshardware.com/uk/reviews/intel-core-i9-9900ks-special-edition-review

Running your chip at 4.9GHz and 1.24v is still pretty damn good for now!