CPU Energy Efficiency for Prime95

[Uncwilly]

Originally Posted by axn

Very nice. How was the power measured?

It says with a Kill-a-Watt on the table.

[axn]

Originally Posted by Uncwilly

It says with a Kill-a-Watt on the table.

Ah, missed that.

[M344587487]

Originally Posted by scan80269

Here are two of my systems running Prime95 with AC power consumption measured using Watts-Up Pro meters:

System #1
- Intel NUC8i7BEH
- Intel Core i7-8559U CPU (28W TDP)
- 16GB DDR4-2133 memory (2 x Samsung 8GB 2133 2Rx8 SODIMM, CL15, CR=1T)
- Samsung 850 PRO 256GB SATA SSD
- Akasa Turing fanless chassis

4 cores 1 worker
PRP exponent 86831357, FFT=4608K
ms/iter: 5.736
AC power: 47.2W

System #2
- ASRock Z390M-ITX/ac motherboard
- Intel Core i9-9900T CPU (35W TDP)
- Nofan CR-95C passive heatsink (black pearl)
- 32GB DDR4-3600 memory (2 x Corsair 16GB 3600 2Rx8 UDIMM, CL17, CR=2T)
- Samsung SM961 512GB NVMe PCIe SSD
- Seasonic Prime Titanium 600W fanless power supply
- ThermalTake Core P1 chassis

8 cores 1 worker
PRP exponent 86846297, FFT=4608K
ms/iter: 4.513
AC power: 59.6W

Both systems are running headless: no display, keyboard or mouse attached.

The second system draws more power from the wall than the first system, but cranks faster. Efficiency wise (iters/watt) they are quite similar.

Here's my 4700u results tuned for efficiency:
8 cores 1 worker
PRP exponent 86846297, FFT=4608K
ms/iter: 8.1
AC power: 20.5W
it/j: 6.02

The small cache hurts throughput but the efficiency is nice. Measured at the wall at 0.5W resolution, ran the test for a few hours to let the it/s settle (I think thermal saturation came into play as it was ~7.8 ms/it initially and slowly creeped up to 8.1). 11W chip power target, headless, 2x16GB 3200 CL22, tlp enabled in bat mode, fan set to performance, 1TB NVMe. With ethernet wifi and blueooth enabled it's ~21W, with bluetooth disabled it's ~20.5W and with everything disabled it's ~20W. When everything was disabled power was measured with everything unplugged.

Much better it/j than the above intel parts but still very poor compared to an R7 no doubt. The CPU in the newest intel laptop part the i7-1165G7 generally performs much worse than Zen 2 mobile, but it has more cache so P95 may be an outlier in intels favour. Zen 3 desktop parts next month and mobile parts next year are the ones to watch.

Someone come out with an APU with an integrated stack of HBM2e already and stick it on an SBC or SFF.

[Viliam Furik]

Originally Posted by M344587487

Here's my 4700u results tuned for efficiency:

If it's a CPU in a laptop, does it even make sense to measure the power consumption at the wall? You are in fact measuring the speed at which the battery charges (which should be almost constant, as the AC adapter is made to do so), and unless the laptop circuitry can direct power around the battery when plugged in, it is not useful at all, IMO.

Try the same experiment with CPU idling. If it pulls 20.5 W, it is only made to charge the battery at an almost constant rate, and I was right.

If it pulls significantly less (<15W), it can direct the power around the battery, you realized the measurement correctly, and I feel terribly stupid.

Based on the AMD site, the CPU can pull up to 25 W, despite the 15 W TDP.

[M344587487]

It's an Asus PN50, an SFF PC using laptop components, no battery or screen, with an external power brick like a laptop. By default the chip's configured to use 25W in it's boost state for a few minutes before dropping to 15W sustained, the defaults can be set by the manufacturer to match their cooler. I've set every power target to 11W for efficiency.



Even if it was a CPU in a laptop I'd argue power at the wall is a valid way to measure as long as you measure for a long-enough period of time to average any inconsistencies away. In the end all power consumed is power the laptop spends, a battery to maintain is just another variable like extra peripherals, different motherboards with different quality VRMS and different quality PSUs. That said, I'm pretty sure that unless you catch the battery in a discharge recharge cycle (automatic maintenance), the battery can be removed as a factor.

[Viliam Furik]

Originally Posted by M344587487

It's an Asus PN50...

Oh, then I am sorry. We have a saying "I am sprinkling ash onto my head." - rough translation. I've found out there is a similar idiom in English - "Eat a humble pie." Anyway, I think you've got the point.

Originally Posted by M344587487

Even if it was a CPU in a laptop I'd argue power at the wall is a valid way to measure...

I still don't think that would be a valid measurement. I will do an experiment soon, with my pretty old Sandy Bridge laptop. I will post the results when it's done.

[DrobinsonPE]

My next efficiency tuning challenge is a computer that I have a GTX 1650 Super GPU in. I previously tried setting different power levels using nvidia-smi -pl and at the suggestion of one of the forum members locked the gpu to the base clock using nvidia-smi -lgc 1530.

Using the -lgc command to set the gpu fequency, I recorded mfakto output, power use, and gpu temperature.

I ended up setting the gpu at 1350MHz because with a 79W total power draw, it can run continuous instead of only running at night.

Total power reduction so far:
i3-9100 - 85W to 46W = 39W savings
GTX-1650 S - 145W to 79W = 66W savings

See the attached picture for details.

[DrobinsonPE]

No one mentioned that my previous results were for a GPU not a CPU. However, to cover up that sin, I did include some information about mprime on the CPU in the picture so I at least pretended to be on subject for this thread.

To redeem myself, Here is efficiency data on an i5-8250U. This is not a laptop. It is a Gigabyte Brix, "NUC" style computer. Interesting to note, the processor is already optimized and as the results show, there really was no significant gain in efficiency by lowering the CPU frequency. Therefore, I will continue to run it at top speed until the fan dies.

Total power reduction so far:
i3-9100 - 85W to 46W = 39W savings
GTX-1650 S - 145W to 79W = 66W savings
i5-8250U - 30.5W to 30.5W = 0W savings

See the attached picture for details.

[retina]

Originally Posted by DrobinsonPE

i3-9100 - 85W to 46W = 39W savings
GTX-1650 S - 145W to 79W = 66W savings

Based upon the rule-of-thumb of USD1 per year for each watt then you will have $105 in your pocket in one year from now.

[kruoli]

Originally Posted by Viliam Furik

"I am sprinkling ash onto my head."

"Asche auf mein Haupt", we have that, too.

[DrobinsonPE]

Originally Posted by retina

Based upon the rule-of-thumb of USD1 per year for each watt then you will have $105 in your pocket in one year from now.

I wish I lived in the rule-of-thumb area of the USA. Some areas of the USA pay a lot more than that.

The utility company I am forced to deal with charges about $0.25 per kWh for baseline use and $0.306 per kWh for tier 2 use. It is a safe assumption that my household uses all of the baseline power so any power used for "extra" non essential use come at the tier 2 rate.

1W*24H/D*365D/Y=8760W/Y
8760W/Y/1000W/kW=8.76kW/Y
8.76kW/Y*0.306$/kWh=$2.68

1 watt for 1 year is $2.68 for me.

At $0.306 per kWh, 250W continuous equals 6 kWh/day. That is $1.84 per day.

My goal is to stay at or under that number. Anything higher than that and my already expensive utility bill starts looking too much like a mortgage.

i3-9100 - 46W
GTX-1650 S - 79W
i5-8250U - 30.5W
J4105 - 20W
Ryzen 3-3200G - 75W

I am currently at 250.5W. If I want to build another computer...I either need to lower my current power use or get rid of a less efficient computer.

that is the problem. How to justify building the next one.

Next up is the Ryzen 3-3200G.