Lowering idle power on Zen 4?

[rubiconlexicon]

I've been tinkering with my 7700X in an attempt to lower idle power. So far I've shaved 6W off SOC (from ~11W to ~5W) by lowering SOC voltage to 935mV. I also seem to have shaved some extra power off elsewhere by lowering both VDDG voltages to their lowest possible value of 650mV. All of this is stable so far (y-cruncher, CoreCycler, and plenty of time spent at idle waiting for idle crashes). After this I tried messing with VDDP, VDDR_MISC, and even dropping RAM to JEDEC, but none of these reduced power. Have I already done all I can to reduce idle power consumption or is there something else to extract further gains?

 

[AusWolf]

Wait a second... You had a VSOC of just 935 mV with EXPO RAM? Was it stable?

Running my RAM at JEDEC gives me an auto VSOC of 1 V. This is basically the best (and only?) way to decrease idle power as far as I know.

 

[rubiconlexicon]

Wait a second... You had a VSOC of just 935 mV with EXPO RAM? Was it stable?

Running my RAM at JEDEC gives me an auto VSOC of 1 V. This is basically the best (and only?) way to decrease idle power as far as I know.

Indeed, no crashing in y-cruncher, no WHEA errors, no idle or game crashes in multiple days. It is stable. My RAM config is EXPO II, 1.35V on VDD and VDDQ, and 6000MHz on a B650E-F with AGESA 1.2.0.0a fwiw. It does seem that I have a good sample when it comes to SOC voltage.

 

[AusWolf]

Indeed, no crashing in y-cruncher, no WHEA errors, no idle or game crashes in multiple days. It is stable. My RAM config is EXPO II, 1.35V on VDD and VDDQ, and 6000MHz on a B650E-F with AGESA 1.2.0.0a fwiw. It does seem that I have a good sample when it comes to SOC voltage.

Indeed, although I haven't had the courage to try under 1 V with EXPO on mine. It can do 1.2 V without problems. Auto gives me 1.3 V with EXPO (it's way too much), or 1 V at JEDEC (this is what I'm currently on) on my board. Compared to EXPO with auto voltage, this is at least 10 W lower at idle.

 

[jxdking]

Nice cpu that can run soc so low.
To get absolute low idle power, get a 8700G instead. Chiplets design like 7700x wastes lots of energy on communicating between chiplets.

 

[freeagent]

When I run my ram at stock 3200C14 on my 58X3D I run VSOC at .875v

 

[AusWolf]

Nice cpu that can run soc so low.
To get absolute low idle power, get a 8700G instead. Chiplets design like 7700x wastes lots of energy on communicating between chiplets.

Either that, or run your RAM at JEDEC speed and your SoC at 1 V. That lowers power consumption by about 10 W on my system, while the performance loss is non-detectable thanks to the 3D cache and GPU-limit with the 6750 XT.

 

[Launcestonian]

Nice cpu that can run soc so low.
To get absolute low idle power, get a 8700G instead. Chiplets design like 7700x wastes lots of energy on communicating between chiplets.

But the 7700X is a single chiplet design, aka CCD, however agree on the suggestion for 8000 series.

 

[AusWolf]

But the 7700X is a single chiplet design, aka CCD, however agree on the suggestion for 8000 series.

It doesn't matter if it's single or dual CCD. It's the IO die that eats 90-95% of your power at idle, especially with high-speed RAM paired with high MC clock and SoC voltage.

 

[tabascosauz]

It doesn't matter if it's single or dual CCD. It's the IO die that eats 90-95% of your power at idle, especially with high-speed RAM paired with high MC clock and SoC voltage.

Much of the idle power is still unaccounted for by Core or SOC, it's somewhere else, presumably from the actual interconnect outside the dies. This hasn't really changed since Zen 2 - APUs both have the lowest SOC draw and also less of that miscellaneous waste.

Indeed, no crashing in y-cruncher, no WHEA errors, no idle or game crashes in multiple days. It is stable. My RAM config is EXPO II, 1.35V on VDD and VDDQ, and 6000MHz on a B650E-F with AGESA 1.2.0.0a fwiw. It does seem that I have a good sample when it comes to SOC voltage.

Nice results. I think I'm pretty much stuck at 1.0V at the very lowest for 2166FCLK 3000UCLK. 2166 might be causing it to quit any lower than that

Lowering PLL may or may not have had a small difference on AM4. Dunno if it's still there on this platform.

Also not sure if VDDIO_MEM_S3 (the UMC voltage) has an impact on SOC power. Last I checked I think I was running 1.3V VDD, 1.25V VDDQ and 1.25V MEM_S3 for my 6000CL30 profile.

 

[AusWolf]

Much of the idle power is still unaccounted for by Core or SOC, it's somewhere else, presumably from the actual interconnect outside the dies. This hasn't really changed since Zen 2 - APUs both have the lowest SOC draw and also less of that miscellaneous waste.

I don't disagree. I'm just saying that lowering your RAM speed, MC clock and SoC voltage has dramatic effect on your power consumption.

For example, running 4800 instead of 6000 MHz RAM and 1 VSOC instead of 1.3 on my 7800X3D lowers idle power from 30 to 17-18 W. Sure, it doesn't explain where that 18 W comes from, but still...

 

[Zach_01]

Much of the idle power is still unaccounted for by Core or SOC, it's somewhere else, presumably from the actual interconnect outside the dies. This hasn't really changed since Zen 2 - APUs both have the lowest SOC draw and also less of that miscellaneous waste.

Yup, that is exactly the case

Look at my Zen3 having avg Core power 18W and ang SoC power 18W but total (PPT) is 50W
Core+SoC is indeed 36W
There are ~14W on "other" stuff that there is no dedicated sensor.

 

[QuietBob]

The number of memory modules and ranks also affect CPU idle power draw regardless of Vsoc. Here's Zen 2 with 2xSR vs. Zen 3 with 4xSR:

Not quite an apples to apples comparison, since the two systems utilize different RAM and timings. Still, on the 5800X3D minimum SoC power draw is about 5 W higher despite considerably lower voltage.

 

[tabascosauz]

The number of memory modules and ranks also affect CPU idle power draw regardless of Vsoc. Here's Zen 2 with 2xSR vs. Zen 3 with 4xSR:

View attachment 365042View attachment 365043

Not quite an apples to apples comparison, since the two systems utilize different RAM and timings. Still, on the 5800X3D minimum SoC power draw is about 5 W higher despite considerably lower voltage.

Hard to compare like that though across different CPUs. Even samples of the same SKU will vary greatly in SOC power, sometimes even across BIOSes.