Should i leave Global C-States Disabled by default?

[Waldorf]

While being a bit older thread, i came across it and others might too, so some "corrections".
those that arent using/building ryzen systems: stop recommending things based on intel, it usually doesnt go well.

for any ryzen cpu, C states enabled is one of the causes for usb/IO problems as well as low load/idle crashing of OS (mainly older gens/older psu).

same for power plans, use ryzen balanced, maybe a customized power saving (for mobile hw/using UPS), high/extreme are a waste, no matter what.

one thing should be done, even on balanced plan (havent checked if recent plan updates already did so), change the min cpu perf to 99% (max still 100), so the cpu is handling clock stuff, not windows.
any usb/pcie power saving option should be disabled, but that's in general for any desktop use, no matter the cpu.

[Slender]

intel:
23h2 - disable c-state cause little increase kernel timer latency
enable c-state + c0 make better.
24h2 - enable c-state cause bad timer kernel latency, disable c-state fix it and feel like 23h2 dis cstate.

[lolokaa]

While being a bit older thread, i came across it and others might too, so some "corrections".
those that arent using/building ryzen systems: stop recommending things based on intel, it usually doesnt go well.

for any ryzen cpu, C states enabled is one of the causes for usb/IO problems as well as low load/idle crashing of OS (mainly older gens/older psu).

same for power plans, use ryzen balanced, maybe a customized power saving (for mobile hw/using UPS), high/extreme are a waste, no matter what.

one thing should be done, even on balanced plan (havent checked if recent plan updates already did so), change the min cpu perf to 99% (max still 100), so the cpu is handling clock stuff, not windows.
any usb/pcie power saving option should be disabled, but that's in general for any desktop use, no matter the cpu.

Can you elaborate on your statement about setting the minimum processor state to 99% instead of 100%? I did some testing last night and could see no measurable difference between the two.

[Waldorf]

Its based on how the internals work on ryzen, and amd recommending to let the chip deal with things (clock), not windows.

high/ultra perf with 100% for min cpu perf are useless short of troubleshooting, so for most users the minimum would be 0 or 50% depending on power profile used, setting it to 99% means windows can still tell the cpu to downclock, but not have a negative impact on perf/response you see from using <99% for min perf.

[JimCarry]

Its based on how the internals work on ryzen, and amd recommending to let the chip deal with things (clock), not windows.

high/ultra perf with 100% for min cpu perf are useless short of troubleshooting, so for most users the minimum would be 0 or 50% depending on power profile used, setting it to 99% means windows can still tell the cpu to downclock, but not have a negative impact on perf/response you see from using <99% for min perf.

so let me get this right,if i have ryzen 5 cpu i must disable c-states,then go to power options in control panel,then change some option to 99%,can you show us picture please ?

[lolokaa]

Its based on how the internals work on ryzen, and amd recommending to let the chip deal with things (clock), not windows.

high/ultra perf with 100% for min cpu perf are useless short of troubleshooting, so for most users the minimum would be 0 or 50% depending on power profile used, setting it to 99% means windows can still tell the cpu to downclock, but not have a negative impact on perf/response you see from using <99% for min perf.

Appreciate the response, but can you provide the source(s) for your claim? To correct myself: I do find a measurable difference, but that's DPC latency in LatencyMon. Running same conditions, on cold boot. From 0,9mcrs (100-100% to) to a consistent 5,0mcrs (99-100%).

[Waldorf]

C-State doesnt have to be disabled, its a "fix" and as long as you dont have usb/bsod/win errors issues, you can leave it on.

for proper power plan adjustment go to control panel, use the one listed as amd, if there isnt one use balanced,
go to change adv power settings, scroll to proc power mng, enter 99% for min, and 100% for max, set cooling to active for both.

[lolokaa]

C-State doesnt have to be disabled, its a "fix" and as long as you dont have usb/bsod/win errors issues, you can leave it on.

for proper power plan adjustment go to control panel, use the one listed as amd, if there isnt one use balanced,
go to change adv power settings, scroll to proc power mng, enter 99% for min, and 100% for max, set cooling to active for both.

I did this for my desktop for my 5900X and both my displays began producing visual glitches, broken pixels, letters inside words disappearing etc... set it back to 100%-100% and it disappeared. Reproduced every time if I set minimum to 99%.

[JimCarry]

C-State doesnt have to be disabled, its a "fix" and as long as you dont have usb/bsod/win errors issues, you can leave it on.

for proper power plan adjustment go to control panel, use the one listed as amd, if there isnt one use balanced,
go to change adv power settings, scroll to proc power mng, enter 99% for min, and 100% for max, set cooling to active for both.

Thanks for showing/explaining,i have only ultimate power plan i have deleted all other power plans,i have also c-state disabled in bios,and also win10 last version,did i do the right stuff ?

[lolokaa]

I would advise against doing this. There is a measureable difference in DPC latency when you do this, and through my testing, when setting the min. to 99%, every time (Ultimate plan)-- the displays began producing visual glitches, "pixelated boxes" flickering, random letters in text appearing and disappearing, etc. At least, on an AMD system (5900X) with an RTX 3080, this is something you should avoid.

I ask of the guy who posted the claim about min.99-max100% to share with us his sources on the claim that this is necessary and/or beneficial in relation to the CPU and OS handling the clocks.