Power supplies for 6 or 7 GPU system

[torin3]

I've been thinking about how to set up PSUs for my new 6 or 7 GPU system. The GPUs are going to be 1080Tis to 3080Tis.

I've been running my 4 GPU system with 2 1KW Corsair PSUs, and that seems to be doing pretty well.

So I was thinking that using one of them, and getting a 1.6KW EVGA PSU for the other, that should be enough.

However, I see there is a massive sale going on now, and I can get them for half price.

Is there enough difference between the G+, PP, P+, or T2 models that I should get one of the more expensive models, or just go with the G+ model for $220?

And given they're so low priced right now, should I just get 2 right now and not mix older and newer hardware?

 

[Zerileous]

If the G+ are essentially the next iteration of the G2/G3 I don't see a problem with them. The thing to consider in this use case is that the power output will be constant. I will admit I'm not familiar with the newer models, but if the major difference is the 80+ efficiency rating, it really depends on how much electricity costs you.

Lets say that overall draw from the GPUs folding is 200w average or 1200w total, since I'm guessing you'll have them under-clocked and under-volted. I'm not sure 3.2KW is necessary, but you'll have a better idea of actual power draw of the system. Most 80+ PSUs are most efficient around 50% load, Edit: I don't actually know at what load these PSUs are most efficient, I can only quote the 80+ rating standards that indicate 50% is the highest required efficiency. These could possibly exceed that. If you're targeting efficiency you may get the most out of running a 1.6KW load on a 3.2KW PSU config. At 50% load a gold is 90% efficient, platinum 92% efficient and titanium 94%. https://en.wikipedia.org/wiki/80_Plus

So to do the math, a gold 1.6KW will pull about 890w to supply 800w, platinum about 875w, and titanium about 850w. So the difference between gold and titanium (in the hypothetical 1.6kw rig) would be about 100w. That's 2.4KWh per day. In the US the average cost per KWh is about 14 cents. https://www.chooseenergy.com/electricity-rates-by-state/. That's about $122 a year.

So for most users no, going for more than gold doesn't make cents (see what I did there), but if they are only $40 more (this is crazy) than the gold and you're going to be running this farm 24/7 for years, and you pay near or more than the US average energy cost, and if all of my reasoning and math is correct, then it does make sense for you.

 

[EarthDog]

Great post, Z!

If it's down to dollars and cents, you need to work the math out. At a high level, generally, you won't make up the large difference between a gold and titanium, for example.

Efficiency curves are so 'flat' and due to 80+ tiers, the WORST case difference between any point (above idle, of course) is 3%...typically 1-2%. So paying so much more for a higher efficiency rating or say, 1600W when 1200W is fine is generally not recovered. Just depends on the price you can get them for as Z said.

 

[BugFreak]

From what I understand eVGA changed their manufacturer on the newer PSUs. I'll try to find the info but if I remember right it isn't the same build quality in general. Not that it would impact it too much but it might not last as long.

To save a little cash you could go with this Seasonic which is also gold.

 

[torin3]

From what I understand eVGA changed their manufacturer on the newer PSUs. I'll try to find the info but if I remember right it isn't the same build quality in general. Not that it would impact it too much but it might not last as long.

To save a little cash you could go with this Seasonic which is also gold.

Well, the Seasonic is only 1KW, not 1.6KW, which will also affect the calculations.

Thanks for the note on the change in build source for EVGA. I bought a new 1KW unit to go along with a video card donation to a webcomic artist I like, and a couple of days later, either the PSU died and took out their motherboard and hard drives, or the motherboard died and killed the PSU. It is across the country from me so I can't check it out personally, but apparently the PSU now rattles when moved.

The warranty on the ones I'm looking at are all 10 years though. Maybe they are selling off the old stock? But given I'm looking at about a 30% increase in my power bill to about $400 a month, I'm going to probably get 2 of the T2 units. (assuming they'll be available).

Thank you everybody!