AWG: Another thing to consider when buying a PSU besides wattage

[UsandThem]

So I recently bought a Seasonic 750w Prime Ultra Gold PSU (build quality and quietness is a thing of beauty). I had been using a 550w Focus Plus Platinum unit that was also a good unit, but I wanted to run two GPUs in my main PC for Folding@Home.

So the unit arrives and install it. When getting ready to plug in my PCIe power cables (the unit came with two PCIe cables with a total of 4 x 6/8 pin connectors), I see this in the instructions for GPUs 225w<:

So it appears since Seasonic went with 18 AWG cables instead of 16 AWG, I had to use one 8-pin connector from each cable, leaving me with no left-over PCIe cables. Right now with the GTX 1080ti I am only pulling around 325w (whole system load) while Folding@Home, so I have plenty of headroom left on the PSU. Since PSU cables are specific to the unit, I either have to buy additional PCIe cables or scrap the dual GPU plans all together. If I would have noticed this warning while researching potential units, I would have instead gone with the EVGA G3 750w which comes with 6 x 6/8 pin connectors which are 16 AWG, and could have easily handled what I had planned to do.

Edit: 3/17/2018

The EVGA G3 750w unit also has 18 AWG PCIe cables, however they include two individual cables each with a 6/8 pin connector for powering high-power cards, and then include a separate PCIe cables that can be used for another card. So despite the EVGA going off-sale, I should have gone with it. Live and learn, and maybe someone else will read this and it will save them some time.

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story2&reid=500

Fortunately, EVGA does in fact provide for the power draw demands of higher powered cards. There are two single connector PCIe cables. Use them both for the watt monsters. This is what talked me out of scoring against Seasonic for the 18 gauge thing on the Primes. Will I feel the need to score on it this time? Let me think about it.

 

[UsandThem]

I actually just found an interesting article on this issue.

http://www.tomshardware.com/reviews/graphics-card-power-supply-balance,3979-6.html

This is my first top-end GPU in probably at least 12 years, so it's on me for not noticing the AWG before buying the Seasonic. It's a great PSU otherwise, I just wish they had used thicker AWG at least on their Prime series, because they aren't cheap power supplies and are built and marketed as the 'best of the best'.

 

[MrTeal]

Honestly, even if you were using 16 AWG I wouldn't recommend using the last method with a high power GPU and a modular PSU. Oftentimes on the PSU side you'll only have three connector pairs on the cable, which is a huge weak point if you're trying to pull 300W through it. 16 gauge cabling would help with heat dissipation, but the connectors themselves are an issue and usually where you see things melting in my experience.

 

[UsandThem]

Honestly, even if you were using 16 AWG I wouldn't recommend using the last method with a high power GPU and a modular PSU. Oftentimes on the PSU side you'll only have three connector pairs on the cable, which is a huge weak point if you're trying to pull 300W through it. 16 gauge cabling would help with heat dissipation, but the connectors themselves are an issue and usually where you see things melting in my experience.

Yeah, that's what I've seen reading various articles/posts (especially from miners). There are quite a few complaints about their cables/connectors melting. I originally was going to put a GTX 1070 and GTX 1080 in with the Prime PSU, but then at the last moment I decided to bite the bullet, and got the GTX 1080ti. Not only that, but the FTW3 model that EVGA states can pull 280w (although I'm not pulling that amount folding).

Like I mentioned, I haven't bought a high-end card for quite a while, so the mistake is on me. I calculated the PSU size correctly where I needed it to run around 60-70% of it's max, but I failed to pay attention to the individual load of the FTW3 on the PCIe cable. I still have 3 PCIe connectors available on the PSU, so I could always order extra cables, but I'm just not sure at this point which route I want to go.

 

[Micrornd]

Good observation and something many reviewers leave out in their rush to praise name brands.

One other thing you may want to mention is to balance or distribute the loads on a multi-rail PSU.
I've seen many folks complain (needlessly) about name brand high wattage multi-rail PSUs due to exceeding a rails limit and causing an overload/shutdown of the PSU, when simply distributing the loads would have left a surplus of power available.

Also all PSU (and UPS) manufacturers recommend sustained loads not to exceed 80% of capacity (with the remaining 20% for peaks and surges). I see many folks push the limits to almost 100%, just to save a few $.

 

[UsandThem]

That's true about making sure there is enough amps on the 12v rail(s). The two PSUs I was comparing both have single 12v rails that can output almost the entire amount of the PSU. However, since Seasonic only ships the 750w with two PCIe cables, right now I cant access almost the remaining 420w I have left. The PCIe slot power cards up to 75w, and each 8-pin connector is good for up to 150w as long as the wiring is thick enough, and like MrTeal pointed out, they actually have enough connector pairs going to each connector. Otherwise the cable/connector overheats and melts.

I almost wish Seasonic had just shipped 4 single cables with only one 6/8 pin on each cable. That way I could have plugged two cables into the 1080ti, and then I could have plugged another 8 pin into the other card I wanted to put in there. But as they say, hindsight is 20/20.

I'm with you about not going over 80% of the capacity on a unit that will be run 24/7. Many of the top end power supplies can actually run for short periods above their stated rating before powering off for safety, but it's not something I would personally allow to happen because it will shorten the life of the PSU if it happens often enough.

 

[ao_ika_red]

Here's a wild option. How about converting 2 of your Molex connectors into one 8 pin PEG connector? It obviously isn't recommended for your gpu but by only having stock core clock and reducing its voltage just above its minimum, I guess the power load will be reduced on those cables.
Of course all of the above is nothing more than crazy thought from me.

 

[UsandThem]

Here's a wild option. How about converting 2 of your Molex connectors into one 8 pin PEG connector? It obviously isn't recommended for your gpu but by only having stock core clock and reducing its voltage just above its minimum, I guess the power load will be reduced on those cables.
Of course all of the above is nothing more than crazy thought from me.

I read a little bit about using a molex adapter, but with some of the horror stories I read, I decided it wasn't worth the risk. Knowing my luck, I'd do it and blow out my entire PC.

Right now I'm deciding if want to order some PCIe cables and putting my 1070 in there, or just leave the 1080ti as the sole card and maybe build a cheap F@H PC for the other card (since I already have so many spare parts). The 1080ti is netting me over a million PPD by itself, so it's pretty good by itself.

 

[ao_ika_red]

I read a little bit about using a molex adapter, but with some of the horror stories I read, I decided it wasn't worth the risk.

That's why I call it an wild option.

build a cheap F@H PC for the other card (since I already have so many spare parts)

If you need some board and cpu, markfw and VirtualLarry have some offer on DC forum.

 

[UsandThem]

That's why I call it an wild option.

If you need some board and cpu, markfw and VirtualLarry have some offer on DC forum.

Thanks, I'll check it out. It sucks because I just sold an i3 CPU and DDR3 a few months back that I should have kept. But that's the way it always works it seems like.

 

[ao_ika_red]

I could see that you want to do space saving and having a more efficient PPD machine but unfortunately your psu doesn't agree with you.

Another option is looking for beefier psu that able to support 4 8-pin PEG connector.
By selling your current psu and grabbing a better one on sale, I'm pretty sure the cost of ownership will be minimal rather than having a full system altogether.

 

[UsandThem]

I could see that you want to do space saving and having a more efficient PPD machine but unfortunately your psu doesn't agree with you.

Another option is looking for beefier psu that able to support 4 8-pin PEG connector.
By selling your current psu and grabbing a better one on sale, I'm pretty sure the cost of ownership will be minimal rather than having a full system altogether.

True, but adding a card like a 1070 would only be around another 140w-150w max at stock, and I have plenty of overhead left. I still have 3 free PCIe connections on the back of my PSU, so if I buy some cables it shouldn't be an issue for the current PSU (425 watts still free). I think Seasonic is just very conservative on what they provide as far as cabling. It just sucks buying after-market cables because so far all the ones I see are pretty pricey.

But I still just have to mull it over for a few days before I decide. Maybe I will see a Ryzen combo deal too good to pass up since their next gen CPUs are being released soon.

HP actually sells a pre-built gaming Omen PC with dual GTX 1080ti cards, and it ships with a 750w Delta PSU.

 

[ao_ika_red]

It just sucks buying after-market cables because so far all the ones I see are pricey.

A big nod to that. There's some cheaper option on aliexpress, but dealing with Chinese seller sometimes is quite exhausting, not to mention shipping cost and stuff.

HP actually sells a pre-built gaming Omen PC with dual GTX 1080ti cards, and it ships with a 750w bronze Delta PSU.

1. HP believe majority of its buyers won't use it 24/7 as folders do.
2. For years, I've heard rumour saying that OEM used low efficiency rated psu but the innard of psu itself actually capable achieving higher efficiency to avoid certification cost (like having its psu certified as Bronze psu but actually capable reaching Silver or Gold level of efficiency). It's just a rumour anyway, take it with a suitable amount of NaCl.