Lowering quite high TDP of CPU by significant amount - Page 1
Forum section: electronics / projects

author: marhuum
author_rank: Contributor
timestamp: September 18, 2023, 05:47:22 pm
content: Can we reliably, simply lower 65 TDP CPU rather significantly so to be as ~ 25 TDP,how actually is the definitive rule in managing to lower such electronic system in physics/science principal

author: coromonadalix
author_rank: Super Contributor
timestamp: September 18, 2023, 06:09:08 pm
content: you lower the clock, or processes, or optimizationor you mean heat sinking ??

author: Someone
author_rank: Super Contributor
timestamp: September 18, 2023, 09:53:07 pm
content: Quote from: coromonadalix on September 18, 2023, 06:09:08 pmTDP .... 65W... CPU... thems consumer desktop speak.Go the opposite direction to overclocking: reduce voltage, reduce frequencyhttps://en.wikipedia.org/wiki/Underclockinginternet search keywords would be downvolting or undervolting

author: macboy
author_rank: Super Contributor
timestamp: September 19, 2023, 01:53:55 am
content: Let's get this straight right off the start: TDP is not a unit. The unit is watts, W. So 65 W TDP, or Thermal Design Power. This is used by the system engineer to determine the heatsink required to cool the CPU in the worst case. It is not the amount of power that the CPU uses all the time.You can significantly reduce power consumption by reducing the frequency and then reducing the voltage as low as possible. Higher speed requires more voltage. The amount of power consumed is proportional to the speed but also proportional to the voltage squared. So reducing speed just a little (and voltage too since you can) will reduce power a lot.If you are running Windows you can go into power settings and change the maximum CPU power state to say 60% or whatever you need to accomplish what you want. In Linux, change cpufreq parameters in the /sys file system. Other O/S with power management will have something similar, or make changes in the BIOS/EFI.

author: metebalci
author_rank: Frequent Contributor
timestamp: September 19, 2023, 05:43:05 am
content: If not modifying something externally, the only way I think is to manually control the P state register (normally it is OS or hardware controlled) and set it to minimum power state (maximum P value, P0 is highest power), this will change the operating point to decrease the power. I would also disable turbo boost.I dont think it is possible to set a hard TDP limit. EPYC processors have a configurable TDP but the range is very small (~30-40W for 200W TDP).Also, TDP is not the maximum power, the processor can temporarily go higher but TDP is the maximum it can run 24/7 with appropriate cooling.

author: Haenk
author_rank: Super Contributor
timestamp: September 20, 2023, 04:59:17 am
content: Also consider the manufacturer rather uses TDP "classes", not exact ratings, for a set of products. So a TDP "100" might peak at 70W - or at only 40W. You might want to check that in advance. It's just to make sure, assemblers only have to stock and consider a few cooler options.Undervolting will likely have limited options, as the manufacturers already operate at the lowest voltage possible. Downclocking certainly will work.

author: Whales
author_rank: Super Contributor
timestamp: September 20, 2023, 05:49:10 am
content: Quote from: macboy on September 19, 2023, 01:53:55 amN.B. it's not a worst case number, at least not with Intel & AMD in the last 10 years or so.Intel & AMD use it as an approx representation of power draw for meeting the non-boost/turbo specs of the product. These are not the specs you see written in big letters, they're the ones in the fine print. Even then there seems to be some rounding going on

author: David Hess
author_rank: Super Contributor
timestamp: September 20, 2023, 12:30:03 pm
content: Both of my recent Ryzen systems and my Ryzen laptop allow lowering the maximum power. My laptop uses a nominally 25 watt Ryzen 7 5700U however the BIOS happily limits it to 15 or 10 watts depending on the setting, and measurements show that it really does. At 10 watts the speed of a single core is still 4.3 GHz, however with all cores saturated they are limited to like 1.8 or 2.0 GHz.I cannot fine tune my laptop, however my desktops with similar processors have settings in the BIOS to finely control the maximum power either by power or current.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 20, 2023, 12:50:31 pm
content: Quote from: metebalci on September 19, 2023, 05:43:05 amIntel is a bit notorious for crippling their processors. They can run at full speed for a maximum of 20seconds or so, and after that time they throttle down their speed, regardless of temperature. It sort of makes sense for consumers, as they can use that boost to start programs quicker, and once a program is started it is mostly idling and waiting for user input. But the real reason they do this is of course that they do not want these "consumer" processors to compete with their "high end" server processors. I find the idea of using a timer instead of the (already available) temperature sensors for this quite atrocious.And the TPD does not say much about the actual power consumption. My Ryzen 5600G has a TPD of 65Watts, but when I'm doing regular stuff it usually does not use more then around 20Watts. Even while doing tasks such as streaming and decoding video (to a 4k monitor) my PC does not even bother to turn up the rpm of the CPU fan. I built my PC myself, as (nearly) all new PC are bundled with software I despise and will not pay for an I just left the stock fan on my 5600G. It makes quite a lot of noise when my PC is busy and it revvs up, but that happens so rarely that I have not bothered to do anything about it. I even see it as an advantage, as most of the times it is an indication that something is wrong, such as a program getting stuck in a loop.