Not undervolting Vega 64

[ExalyThor]

Back when Vega was the new hotness (pun intended), everyone mentioned undervolting. Well, if cooling isn't a problem, is it worth to undervolt if the main goal is performance? Shouldn't higher voltages enable higher clocks?

[BetteBalterZen]

Using a voltage curve, fx in MSI Afterburner, you can target a higher clockspeed at the same volt the card pulls at stock, kinda enabling higher clockspeeds using undervolt techniques. Or simply target the stock clockspeed at a lower voltage point - making a "real" undervolt. You could of course target lower than stock clockspeeds and achive even better undervolts. 

[Levent]

Depends on what limit you are hitting. On Nvidia cards almost %90 of the time, limit is PWR, in those cases undervolting the card may allow lower power consumption thus allowing the card to boost higher and/or for longer. This also can help with cards with shitty VRMs.

 

[RONOTHAN##]

DISCLAIMER: I've never run a Vega, daily'd mainly Nvidia cards and interested in overclocking Nvidia card. Most of this should transfer over, GPUs are just GPUs, but just for reference.

 

It really depends. Silicon has thermal resistance, and depending on the chips, even if the temp sensors are reporting it being pretty cool, it might actually be running very hot internally and more voltage does not result in more performance. If you're going cold enough (I.E. LN2), it should be cold enough internally for more voltage to result in more stability, but odds are you're not doing LN2. Plus, there are cards like the GTX 1080 that don't actually scale past ~1.3V even when they're on LN2.

 

There's also the issue of power limits. Power = Voltage * current, and current is (more or less) directly related to the clock speed. Since the power has to stay below a certain thresh hold (unless you do a custom vBIOS to remove those limits), lower voltage means that the current can increase for the same amount of power, resulting in higher clocks and more performance. 

[ExalyThor]

So they behave normally? I thought it had some weird reverse scaling with voltage. I'm weighting my future GPU upgrade options, and I want to know more about vega and navi.

[RONOTHAN##]

14 minutes ago, ExalyThor said:

So they behave normally? I thought it had some weird reverse scaling with voltage. I'm weighting my future GPU upgrade options, and I want to know more about vega and navi.

Negative scaling with voltage can occur with other cards, pretty much every Nvidia GPU since Pascal has scaled negatively at ambient with more voltage, though with Vega does seem to scale with voltage if the temps are low enough. It's just that you don't really get proper voltage control with it, so unless you're gonna be volt modding the card, you'll be stuck at 1.2V max.

 

That said, odds are it's not gonna make sense to get a Vega 64, they're priced like RX 6600s on the used market last I checked, and one of those cards should be just overall better.

[ExalyThor]

7 hours ago, RONOTHAN## said:

Negative scaling with voltage can occur with other cards, pretty much every Nvidia GPU since Pascal has scaled negatively at ambient with more voltage, though with Vega does seem to scale with voltage if the temps are low enough. It's just that you don't really get proper voltage control with it, so unless you're gonna be volt modding the card, you'll be stuck at 1.2V max.

 

That said, odds are it's not gonna make sense to get a Vega 64, they're priced like RX 6600s on the used market last I checked, and one of those cards should be just overall better.

I assume (and hope) the used market will implode and they will be cheap again. Today though yeah, used AMD gpus make no sense. Vega 64 is selling for 1080ti prices and 5700xt is selling for 2080S prices. Sadly I can't go the 6600xt route because I'm still rocking my old i7 2600K. I never thought the pcie 2.0 will be a bottleneck because my reasoning was "it's too slow to drive the top end GPUs anyway, it doesn't matter", but then AMD decided to give the 6600xt only 8 lanes, so even though the raw power is there, 8 2.0 lanes are just not enough.