Undervolting RX6800: Unstable voltage

[VZX]

So I've seen several videos/clips from YT of RX 6800 performing at stable 900 mV undervolt and draining about 160W power max.

 

The thing is that I haven't been able to do so with the AMD Adrelanin Performance Tuning.

 

Current setup I'm using is

Core Clock Min: 2275 MHz

Core Clock Max: 2375 MHz

Voltage: 910 mV

Memory Timing: Fast Timing

VRAM Clock: 2112 MHz

 

Zero RPM Fan: enabled

Advanced Fan Control:

- 30°C→35%

- 50°C→45%

- 65°C→60%

- 75°C→80%

- 85°C→100%

Power Limit: 10% (maxed)

 

During load, the Core Clock and VRAM clock were operating within the specified value (VRAM being closer to 2100 MHz and Core Clock is closer to 2350 MHz most of the time). However, the voltage can shoot up to 968 mV and Power drain can reach up to 200W. Only within small window the voltage dropped to 868 mV.

 

So, my immediate tuning would be reduce the voltage from 910 mV to something lower. I treid 900 mV, 890 mV, 880 mV, 870 mV, 860 mV, 850 mV... and nope. 850 mV was too low of a voltage when I'm just using my PC for web-browsing/ watching YT videos. Because it pushed the actual voltage under 800 mV.

 

Even with 910 mV setting, under low usage, the operating voltage actually dropped to 868 mV most of the time instead of staying at 910 mV all the time. 

 

So what if I tune down the core clock? I did try lowering the min and max by 15/25 MHz per step.... Well, it does lower the voltage under load (it can go to just under 916 mV under load), but at the same time, also lower the minimum voltage on low GPU utilization to 830 mV, making the system kinda unstable to the point that AMD Adrenalin got restarted and reverted the tuning back to default setting.

 

So, I'm at loss here, what kind of tuning so that I can get a stable 900 mV under load? Or rather... my concern is actually on power draw: How do I get ~160W power draw with similar performance under stock setting by undervolting?

 

Or maybe the showcases I saw on YT are different under different game?

 

Or maybe that because the newer AMD Adrenaline software no longer gives option of 15% power limit (it's capped at 10% on my this v24.2.1), then I couldn't quite get the result of those old benchmark?

[emosun]

11 minutes ago, VZX said:

So I've seen several videos/clips from YT of RX 6800 performing at stable 900 mV undervolt and draining about 160W power max.

so you saw a video of someone elses silicon doing that , that has zero to do with yours so idk why you think yours has to be able to replicate it.

[Eigenvektor]

It is called silicon lottery for a reason. Some cards will overclock or undervolt better than others.

 

There is no guarantee that your specific card can get the same values or be stable at these values. You can only try to adjust them step by step, testing stability in various games.

 

I've had undervolts that were stable in one game but not another, or only until I hit a specific section of the game. You can only go back, adjust, repeat tests until you can not longer reproduce crashes anywhere.

[WereCat]

What you're trying to achieve is almost impossible with just the Adrenaline software due to how the "Voltage" in that SW behaves as it's not really changing just voltage but the whole voltage/frequency curve and for that reason you'll still get more voltage on high end spectrum of the load as long as there is enough power budget available for the card. Since you can't reduce the power slider far enough the voltage will keep going up while at the lower end it will be unstable as it will remain too low.

 

You'll need to get MPT (More Power Tools) to achieve the best results for what you want as you'll have way more control over various settings not available via the Adrenaline SW.

 

You can set hard power limit to whatever you want.

You have control over Core, SOC and VRAM voltages as well.

 

- Just tweaking SOC voltage without any other changes can shave off 15W-20W depending on how low you can get it. Instability usually occurs by sudden black screens and having to restart PC so it's kind of annoying to get it right sometimes.

 

- VRAM voltage is not worth tweaking as you won't be really saving enough power to justify the hassle, it's worth increasing if you want to push higher VRAM clocks or better VRAM timings.

 

- Core voltage in MPT will hard cap the max available voltage AND you also can hard cap min available voltage for the card unlike what you set in Adrenaline SW and you can actually combine those for best effect. For example you set 900mV in MPT and the card will never go above 900mV then you tweak the Voltage slider in Adrenaline to get lower voltages under less load (if that is stable or when bouncing off of power limit).

Now that I mentioned power limit, if you hard cap voltage in MPT it's unlikely you'll reach the power limit set in Adrenaline SW, still you can even hard cap max power for the card in MPT but I don't recommend it because every time you bounce off of power limit you'll get clock dip. IMO it's better to have the power uncapped and let the card use this power for some irregular peak loads.

 

 

 

 

Now to disadvantages of using MPT and how to use it:

 

- It's a janky SW that is not well documented, I use it and have no problems with it but the way it's distributed and maintained is kind of janky so use at your own risk.

- MPT has so much control that you can brick your card if you start touching stuff you have no idea what it's for (the settings I mentioned are generally fine unless you use some stupidly high or low values).

- All your settings will be gone after driver update or reinstall so you'll have to save a profile to load from if you ever update drivers or reinstall them (if anything goes wrong you can revert settings this way too)

- You need GPU-Z to extract the cards BIOS file then you load that BIOS file into MPT to expose the settings from your card

 

The Power Limit (W) settings is what will be available for the card when you set the Power Limit slider to 0%. So in my example with maxed out slider the card can go up to 345W at +15% in Adrenaline SW with 300W set in MPT.

 

You can reduce these clocks to achieve higher SOC undervolt. These clocks don't affect performance almost at all unless you're pushing high core clock. Feel free to compare results. Typically you'll get more headroom for your core so it will compensate. I'd just tweak the SOC clock personally and leave Fclk at stock but it may keep you from reducing SOC voltage so up to around 100MHz downclock won't really hurt.

No need to touch the min clocks here.

 

You apply the settings by hitting Write SPPT and then restarting the PC.

 

Again for core voltage, don't try to replicate the same settings you've done in Adrenaline SW. Better start lowering it slowly in MPT just in case as the voltage will behave way differently.

[VZX]

3 hours ago, Eigenvektor said:

It is called silicon lottery for a reason. Some cards will overclock or undervolt better than others.

 

There is no guarantee that your specific card can get the same values or be stable at these values. You can only try to adjust them step by step, testing stability in various games.

 

I've had undervolts that were stable in one game but not another, or only until I hit a specific section of the game. You can only go back, adjust, repeat tests until you can not longer reproduce crashes anywhere.

I think you (and the other commenter above you) misunderstood the word 'unstable' I used here.

 

The 'unstable' in the title refers to voltage flip-flopping between  ~-50 mV and  ~+50 mV from the specified voltage I set in the AMD Adrenaline.

 

The 'unstable' here does not mean the system is unstable. I specifically wrote 'the system kinda unstable' to refer this particular occurrence (PC got frozen for a bit and AMD Adrenaline got restarted and reverted everything to default value).

 

So if the the voltage flip-flopping between these 2 extremes (none of which is actually the voltage I specified in AMD Adrenalin), that means I have bad silicon lottery?

 

The actual problem I wish to elminate is the voltage that flip-floping on two extremes. The solution does not necessarily have to be exactly an undervolt setting with 900 mV voltage. I can accept 910, 920, 930, heck or even 940 mV if there's such settings to be made. But the thing is all my attempts have been futile. The voltage still keep flip-flopping.

[-rascal-]

9 hours ago, VZX said:

I think you (and the other commenter above you) misunderstood the word 'unstable' I used here.

 

The 'unstable' in the title refers to voltage flip-flopping between  ~-50 mV and  ~+50 mV from the specified voltage I set in the AMD Adrenaline.

 

The 'unstable' here does not mean the system is unstable. I specifically wrote 'the system kinda unstable' to refer this particular occurrence (PC got frozen for a bit and AMD Adrenaline got restarted and reverted everything to default value).

 

So if the the voltage flip-flopping between these 2 extremes (none of which is actually the voltage I specified in AMD Adrenalin), that means I have bad silicon lottery?

 

The actual problem I wish to elminate is the voltage that flip-floping on two extremes. The solution does not necessarily have to be exactly an undervolt setting with 900 mV voltage. I can accept 910, 920, 930, heck or even 940 mV if there's such settings to be made. But the thing is all my attempts have been futile. The voltage still keep flip-flopping.

 

The +/-50mV would be due to V_DROOP. Under certain circumstances / loads , the GPU would be pulling more current, causing the voltage to droop.

Unlike CPU tweaking, you don't really have any user configurable Load-Line Calibration (LLC) on a graphics card.

 

When AMD Adrenaline crashes / restarts, recovers and reverts to default values, that means it is unstable.

It's not unstable enough for the system to crash, though. The drivers are able intervene and prevent that.

 

The closer the chip is to ideal (e.g. 100% flawless chip), typically, the more optimal.

So, better the silicon quality

• More stable voltage / less V_DROOP
• Better change of undervolt / overvolt
• Able to achieve higher overclock
• Better temperatures
• etc... 

The damn thing with review samples, is they are sometimes "cherry-picked" by the manufacturer.

They screen / bin for the best ones right at the factory.

What you get at retail, "your mileage may vary" applies.

 

It looks like 900 mV is a bit too aggressive for your particular card, so you may need to bump it up slightly...to 910 mV, or 925 mV, etc.

[VZX]

11 hours ago, -rascal- said:

It looks like 900 mV is a bit too aggressive for your particular card, so you may need to bump it up slightly...to 910 mV, or 925 mV, etc.

I also tried this and noticed that the voltage still flip-floping between ~-50 mV and ~+50mV.

 

If I set to 930 mV voltage, then ingame I got flip-flop between 893 mV to 993 mV, with most of the time it's more often stay at 993 mV and power draw is still well above 200W.

 

I well understand that "system unstable" thing, but I just want to eliminate this problem that voltage getting flip-flopped anytime GPU usage changes. i.e. it's near 0% on typical desktop usage, but near 100% during gaming. Meaning that I'll have at ~-50 mV (unstable) during desktop usage, but ~+50 mV (actually drawing more power than expected) during gaming.