Folding Forum

On my system, the CPU still downclocks and even sets cores to idle with cpb and pbo off, although this is hard to see in Windows because task manager just reports the frequency of the most active core. Use AMD's Ryzen Master to confirm things still downclock.

jrweiss wrote:The down side appears to be that the CPU does not downclock at idle. Even so, idle power consumption is still at around 24 Watts, same as with PBO+CPB enabled.

Thanks, I wasn't aware that CPB downclocking does so little to save power. In that case a Ryzen 3 3300X or 2300X might be a better "GPU feeder", because they have only 4 cores switched on. Or perhaps even an i3-10320? Manually undervolting and underclocking might bring the usage lower, but due to stability and reliability of the science result we shouldn't be doing that.

Paragon wrote:On my system, the CPU still downclocks and even sets cores to idle with cpb and pbo off, although this is hard to see in Windows because task manager just reports the frequency of the most active core. Use AMD's Ryzen Master to confirm things still downclock.

On my Ryzen 5 3600 system (Linux Mint 20), the command reports individual thread frequencies like this with CPB off (EZ System Tuner: Asus Optimal, TPU: OC Tuner), idle: CPB off (EZ System Tuner: Asus Optimal, TPU: OC Tuner), GPU folding only: CPB on (EZ System Tuner: Normal, TPU: Keep), GPU folding only: If the CPU behaves the same way as under Windows, then perhaps these are "set" frequencies, and not "get" frequencies?

Something doesn't make sense there. With CPB and PBO off, I still get downclocking on my non-utilized cores. When the machine is idle, a lot of the cores say "sleep" in ryzen master. Even when I'm crunching away, if it's not using all the threads, the unused cores throttle down.

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If you actually measure lower watts drawn by the CPU with a meter, then I'm inclined to believe the clocks reported by Ryzen Master over the Linux kernel; but to confirm that it's correct we should measure it running under Linux to see if the CPU actually behaves differently, or if it's just a difference in reporting. (Some motherboards misreport power draw to trick the CPU into running faster.)

With PBO off, your CPU will run at their stock rated TDP and base frequency.
For a 3900x, that would be 3,5Ghz, and 105W TDP.
It actually consumes slightly less than 105W.

With PBO enabled, it will run at the motherboard's boost frequencies, which will mostly depend on the VRM count, and the amount of 4-pin CPU plugs your motherboard supports.
If you only have 2 of them (8 pins), your CPU will boost to no more than the maximum rated wattage for 8 pins, which is 150W.
Usually that's between 3,8-4,1Ghz, less if you have lousy or cheap VRMs.
If your motherboard has 3x 4-pin, or a 12 pins connector, your CPU can theoretically boost to the frequency at 225W, (depending on the VRMs).
That usually means 4-4.4Ghz on all cores (for a 3900x).

The max boost frequency AMD rates their Ryzen's for, under an all core load, is when 4x4-pins (16pin) CPU connectors are used.
For a 3900x, that would mean, a maximum of 4,4-4,7 Ghz, and usually it can only hold those frequencies for a few tens of seconds, and needs a large water cooling system.

There are 2 settings your CPU can operate efficiently at.
1- PBO disabled. Your CPU will keep itself at base clocks, at the rated TDP.
2- PBO enabled, but with ECO profile enabled.
This ECO setting, you can manually modify in AMD PBO settings, to mimic the stock TDP settings.
By doing so successfully, you can make your CPU run at the stock TDP, but at higher, auto controlled frequencies.
That means depending on the load, your CPU could be running anywhere from 3,5Ghz to 3,75Ghz for a 3900x, using the same wattage.
I would not manually set the CPU frequency, as doing so allows you to overclock ~5% faster than PBO, but you also run into the risk of CPU overclocking errors.
By using PBO, and manually adjusting the ECO settings to your desired TDP, temperature, and Amp draw, you can still run low wattages; but when the load allows (lower load) the CPU could upclock the frequency dynamically, and downclock under heavy loads automatically; without running errors.

gunnarre wrote:If you actually measure lower watts drawn by the CPU with a meter, then I'm inclined to believe the clocks reported by Ryzen Master over the Linux kernel; but to confirm that it's correct we should measure it running under Linux to see if the CPU actually behaves differently, or if it's just a difference in reporting. (Some motherboards misreport power draw to trick the CPU into running faster.)

I'm doing that as part of my series of articles on the 3950x, and it is definitely using less power corresponding to the downclocked CPU states. For example, for a 4-core CPU folding slot (with the rest of the cores either slept out or at lower clock rates according to Ryzen Master), the system is using 140 watts at the wall. The four active cores are hovering around 4220 MHz, and the rest are all under 2000 MHz or report out as "sleep" in Ryzen master. Running this exact same test with core performance boost off, the four active cores are all running at 3500 MHz, and the rest are all under 2000 MHz or report as "sleep" in Ryzen master. Power consumption in this configuration is 92.5 watts, which is a lot less than 140 and corresponds to a much cooler CPU temp.

I can dual boot this machine into Linux and check it out once there once the current round of tests complete

jrweiss wrote:The down side appears to be that the CPU does not downclock at idle. Even so, idle power consumption is still at around 24 Watts, same as with PBO+CPB enabled.

Update: It appears the clocks do reduce slightly at idle, to 3189 (3.2 GHz); and idle power consumption is down to 23 Watts (all info per CPUid HWInfo).

After some help getting my GPU folding from this forum, removing a 140mm fan and adding 3 120mm fans to the front and replacing the stock cooler with a Noctua NHU12-S chromax.Black the temperature is now 72 C at load. It dropped the temperature about 17 degrees. Thanks for all the suggestions.