3900x performs better with pbo off.

[sgoaty]

I just installed my 3900x and have been having a bit of a play around with it.

It seems to perform better (150-200 points better in cinebench) with pbo disabled. It runs around 50mhz faster on all cores and gets around 5-8c hotter.

That's the compete opposite of what I'd expect. Can anyone explain?

Thanks
Scott

 

[alec]

PBO will feed a lot of extra voltage, which in theory should help cores to boost higher and longer. In reality all it does is increase power consumption and heat output, which makes cores downclock instead from hitting temperature and boost power limits.
Keep it off.

Wait for Ryzen ClockTuner to be released next week. It promises higher clocks with undervolt, done right.

 

[henson0115]

I just installed my 3900x and have been having a bit of a play around with it.

It seems to perform better (150-200 points better in cinebench) with pbo disabled. It runs around 50mhz faster on all cores and gets around 5-8c hotter.

That's the compete opposite of what I'd expect. Can anyone explain?

Thanks
Scott

this is also my experience with my 3900x, ive since run it without PBO since launch

 

[FredFlint]

My 3900x ran better with an under volt of -0.1v at first, with the current BIOS im using -0.025v. I have not tried PBO, but it will probably increase temps and reduce boost.

 

[sgoaty]

Did you verify performance with cinebench?
Thanks
Scott

 

[C64]

https://www.guru3d.com/files-details/1usmus-custom-power-plan-for-ryzen-3000-download.html

• Global C-state Control = Enabled
• Power Supply Idle Control = Low Current Idle
• CPPC = Enabled
• CPPC Preferred Cores = Enabled
• AMD Cool'n'Quiet = Enabled
• PPC Adjustment = PState 0
• I also recommend disabling PBO, which activates Precision Boost 2.0 for clock management. This ensures only temperature and FIT play a role for clock speeds.

 

[sgoaty]

https://www.guru3d.com/files-details/1usmus-custom-power-plan-for-ryzen-3000-download.html

I just tried that and lost 300 points on cinebench compared to everything stock except infinity fabric at 1800 to match my ram

 

[muon]

PBO will feed a lot of extra voltage, which in theory should help cores to boost higher and longer. In reality all it does is increase power consumption and heat output, which makes cores downclock instead from hitting temperature and boost power limits.
Keep it off.

Wait for Ryzen ClockTuner to be released next week. It promises higher clocks with undervolt, done right.

Exactly this. PBO has a leg up as you probably aren't pushing as much voltage. PBO is working right up to the power limit (anyone know what is for 125W chips?).

edit: It is 142W.

 

[Sayso]

My CPU has better synthetic scores by leaving PBO off and undervolting!

 

[nutsnut]

Same here, pbo off and 0.102 undervolt scores me 400 more points in cinebench, lowers temps by 10c and only slightly reducing my single core speed by 5-10mhz.

 

[Minstadave]

Mine is the same. Lose 200 points in Cinebench with Pbo on.

 

[555BUK]

My 3900XT is the same. I score 7400-7500 @ stock CPU / memory-only overclock within Cinebench R20 (PBO disabled), and drop ~200 points once PBO is enabled. I was thinking it could be my B450M mobo struggling to deliver the extra power. The mobo's VRM's jump from 50-deg to 90-deg once PBO is enabled.

 

[megatron]

I have unlocked the power limit via a combination of bios settings, I tested PBO off and for me it lowered scores. Maybe these two facts are related?