All things must come to an end - and here that means some snags, tweaking some settings, and a few thoughts on performance:
A few weeks into running the build, I can confirm that everything runs (surprisingly) stable - clearly, it has one giant thermal bottleneck which is the 140mm rad - with that said, both GPU and CPU are designed to work in constant re-evaluation of their thermal environment and testing the thermal limits through constant frequency adjustments anyways, and the system is equalizing nicely in the mid-fifties for water and case temps (yep, it's designed to run "hot"), with GPU and CPU surfing just below thermal limits when under load.
Whilst these latest gen GPUs and CPUs have much less scope for manual overclocking or undervolting, they appear to also very well adapt to their thermal and max out performance with whatever cooling it available.
The benchmark results I get are pretty well-comparable to typical builds whilst slightly on the below-average side of things, so the cooling solution seems to be saturated - in a way that's what I have been after for this SFF build as radiators come at an immense space tax.
Overall, it seams to stabilize and handle the "hot" environment much better than my previous 5950x/ 3090 combo: I have not had a single thermal shutdown, and that's torturing it for hours with ultra settings in MSFS2020 VR until my headset batteries were drained. I had crazy ram temperatures in excess of 105C in my 3090 setup whereas here everything is high but within safe bounds here, and things appear to be well balanced even at simultaneous high CPU and GPU loads.
But more on that later - first to some final touches on the build:
First, I have treated myself to a new Noctua NF-A14 Industrial: The one you see in the build went through numerous iterations and turned into a bit of a skeleton along the way.
With a new one I expect to get a bit more pull and a tighter fit with the radiator - and potentially a bit less noise as the various cuts on the current one all contribute to turbulences.
And this is what will have to give on the new one:
A long slot in the corner for my "bleed air" intake from the PSU, next to it a pocket for the overlap with the 4090's PCB…
…and a pocket on the long side as a conduit for the AC power cable.
About one battery charge of my Dremel later…
I look a this - the minimum viable modification to the NF-A14 with the pocket for the 4090 in the background, and the space for the AC cable in the foreground. You may also note that I have sleeved the coloured fan wires running along the frame for improved blackness. Not entirely sure why Noctua doesn’t do it by default as their factory sleeving does fit nicely in the conduits of the fan.
Tha't how my bleed air port now looks like - a bit smaller than the pervious iteration and precisely matching the PSU's air outlet.
Next, I prepare the edges of the radiator with some super sticky double sided silicone tape (its turning into my universal favourite for fixing anything!) to get things reasonably air tight between fan and radiator…
…and in goes the fan and a cover plate to form a duct between PSU air outlet and the bleed air port of the NF-A14.
Nice!
Another thing I really wanted to add this time is a dust filter:
When taking my old build apart, I noted quite some dust on the radiator's fins- and they are particularly hard to clean.
And as these are the most critical parts to keep clean for good heat dissipation…
…I intend to protect them as good as possible: This generic carbon filter fleece for cooker hoods should do the trick: Not only is it catching a good spectrum of particle sizes whilst having a reasonably low flow resistance, it also comes in a very satisfying shade of pitch black!
This piece of 130x140mm should nicely tuck under the flanges on the frame of the radiator…
…and yes, that's a fit:
Should do the trick!
Last finishing touch is applying some sleeving to my 12AWG power cables:
Whilst they are already reasonably black, they kinda stand out in what has turned out to be a surprisingly clean build given the density of stuff within.
This should be reasonably presentable - I failed to get both wires into one sleeve- the bullets are just a tiny tad too wide…
And ta-daa: Build complete!
Performance
Reading a bit into the behaviour of the 7950X3D, I quicky realise that undervolting it like the 5950X is not really a worthwhile pursuit - the way AMD has made the 3D cache work by is pretty much undervolting the chip automatically, and that way more efficient than I could to it. This also shows in the X3D's significantly lower TDP compared to the 7950X.
So I settle for the full complement of AMD's out-of-the-box tuning kit for the CPU: Expo profile on (my 6000Mhz CL32 ram should pay off here), Precision Boost Overdrive on, ASUS's voltage profile applied, slightly elevating the temperature target to 90C - and that's it!
So what I'm left with for performance tweaking is the GPU: And when I say performance tweaking, it's attempting to drop the power consumption in order to raise performance, as in a thermally bottlenecked system, less load on the cooling solution should increase the frequency boost headroom.
Like with the 7950X3D, the 4090 appears to do much more automatic and on-the-fly optimization for frequency boost targets compared to its predecessor, so manual voltage curves appear to be of little effect, whereas the global power limit would be the more efficient (and also much simpler) way to adjust its behaviour.
I started out with a PPL score of 977k - and going through a number of iterations, I indeed see the GPU performance go up when setting a GPU power limit of <100%.
The sweet spot turns out to be at 85% - see my test table below, benchmarking both CPU and GPU performance with varying settings:
And finally, with a 85% GPU power limit and ASUS' CPU voltage profile applied, plus a CB23-biased boost profile, I get to a PPL score of 1.07M!
Time to post my score… thanks everyone for following here!