I meant extreme as in the most demanding not as in the actual setting sorry, but will a 9900k overclocked only for SSE or a basic O/C however you want to call it draw 30% less power, as the temp guide tells us avx is 30% above normal TDP?! 240W - 30% would be around 170w so it would draw as much as his 8600k under avx/2?
My exact words were "
more than 240 Watts", which, depending upon Vcore, can be a bit conservative for an OC'd 9900K running an AVX workload. The temp guide states at Intel stock settings, P95 Small FFTs with AVX is about 130% workload, or 100% workload without AVX.
stanley88845, instead ran OCCT, CPU, Small, Extreme, Steady, Instruction Set "Auto" (AVX/2), which is about 125% TDP workload. However, while the differences in these tests might seem trivial, when you factor in the differences for 2 additional Cores, 4 additional Threads, 9 MB Cache versus 16 MB Cache, no Hyper-Threading versus Hyper-Threading and differences in Core voltage, that's a lot of variables which all determine the power equation, so the answer isn't straight forward enough to generalize. I'll elaborate below.
The 8600k under the test conditions I put it under is decently similar to the sort of load that a 9900k would put on the vrms on Cinebench R23, right?
Not quite so; again, we need to be
very specific when defining test conditions due to the number of variables involved.
When properly configured for equivalent features, P95 and OCCT have nearly identical workloads and power consumption with AVX / AVX2, or without AVX / AVX2. However, without AVX / AVX2, the same P95 and OCCT tests have power consumption nearly identical to CineBench R23 (as well as R20), although the CineBench workload characteristics differ somewhat from P95 Small and OCCT Small, as detailed in my first post.
If you mean comparing your 6 Core 6 Thread 8600K OC'd to 5.0 @ 1.38 Vcore tested on OCCT with a
synthetic AVX/2 workload at 160 to 170 Watts, to an 8 Core 16 thread 9900K OC'd to 5.0 @ 1.3 Vcore tested on CineBench R23 with an AVX/2
real-world workload at a projected 160 to 170 Watts, then you're guesstimation is a bit low.
A few hours ago I tested an 8600K OC'd to 5.0 @ 1.364 Vcore with OCCT, CPU, Small, Extreme, Steady, Instruction Set Auto (AVX/2), which closely replicates the settings you used.
All tests were run for 10 minutes. OCCT power consumption stabilized at 185 Watts, which differs from the 160 to 170 Watts you posted, possibly due to your test duration being shorter. I then ran your CineBench test, where power consumption stabilized at 128 Watts, which is a bit below the 130 to 140 Watts you posted, possibly due to our test sample running at a slightly lower Vcore. Also, ambient temperature and cooling haven't been mentioned, so it's quite likely that our results differ in those aspects as well.
All tests were performed at 21°C ambient.
Many users are unaware that Core temperatures affect power consumption. As temperature increases, leakage current increases, which in turn increases power consumption. In electronics, although this runs contrary to Ohms Law, where resistance increases with temperature, leakage current more than cancels out the effect. This means hotter CPUs consume more power at the same Vcore than cooler CPUs. Moreover, at Intel stock settings, Hyper-Threading increases power consumption by about 12% and Core temperatures by 4 to 6°C. The difference can be considerably higher depending on how much a CPU is overclocked. Additionally, delidding not only reduces Core temperatures significantly, but in turn, it also reduces power consumption.
We don't happen to have a 9900K at hand just this moment to repeat the tests, nor can I accurately recall previous 9900K test results, however, I tested an 8700K OC'd to 5.0 @ 1.332 Vcore. I repeated your OCCT test, but instead with SSE (no AVX). Power consumption stabilized at 156 Watts. CineBench R23 stabilized at 160 Watts, while Prime95 Small FFTs, no AVX stabilized at 161 Watts. Based on these findings, if we add a proportionate increase in power consumption for the additional Cores, Threads and Cache, then my guesstimate would put your hypothetical 9900K OC'd to 5.0 @ 1.3 Vcore at about 210 Watts, which is a familiar value.
This means that when running a valid 100% workload, your motherboard VRMs will not be capable of supporting the power delivery required to sustain an OC'd 9900K. Nonetheless, I again tested the 8700K, but with CPU-Z > Bench > Stress CPU, which is a steady-state workload at about 80% that's more indicative of peak workloads during games that are highly CPU intensive. (Keep in mind that % CPU Utilization is processor resource activity; NOT actual % TDP workload.) Power consumption stabilized at 123 Watts, which would calculate to about 164 Watts for your hypothetical OC'd 9900K. This suggests that if you limit thermal and stability stress tests to utilities that don't exceed 80% workloads, and you only game without using rendering or transcoding software, then you
might be able to squeeze by.
If you read
Section 11 -
Thermal Test Basics in our
Intel CPU Temperature Guide 2021, as
TerryLaze and I both previously suggested, and look at figure 11-2, which is the %TDP scale, you'll get a better perspective of how much different
steady-state and
fluctuating workloads in stress test utilities can actually vary, which directly impacts power consumption and temperature. For example, while utilities such as CineBench and Asus RealBench run
real-world AVX code, just as does rendering or transcoding software, the
synthetic AVX code in OCCT and Prime95 is much more intense. This is why real-world AVX workloads typically may
approach, but
not exceed, OCCT or P95
without AVX, and is again why
Intel's Datasheets state that TDP and Thermal Specifications are validated without AVX. So even if you run software that uses AVX, it's misleading to enable AVX worloads in test utilities if you expect to see real-world temperature and power consumption values.
The bottom line is that providing you only use your rig for gaming, your present motherboard is marginal, at best, for you to consider upgrading from your 8600K to a 9900K. However, if your case allows enough access to the back of your motherboard, check the screws which fasten the heat sinks to the VRMs to ensure that they're at least snug. Even if you can gain a quarter turn, it may help to drop your VRM temperature several degrees. If you decide to purchase the 9900K, then I suggest that you run CPU-Z > Bench > Stress CPU, which is steady-state workload at about 80% to test thermal performance, and Intel XTU, which is a fluctuating workload that's also about 80% to test stability. By using these particular 80% workload stress tests, your CPU will require less Vcore and consume less power, while you'll still be able to achieve a stable overclock without pushing your VRMs to their thermal throttle limit.
CT
Facebook
Twitter
Instagram