Is the SeaSonic FOCUS GX-850 ATX 3.0 850W compatible and good enough for the RTX 4080 Super?

[Memes]

Friend is getting his PC parts and one of the PSU I recommended was the Be Quiet Pure Power 12M but it ran out of stock so it wouldnt make it on time so the next one I did research on is the SeaSonic FOCUS GX-850 ATX 3.0 850W [pcpartpicker.com]. Would the PSU be good enough and compatible for my friend's build? [pcpartpicker.com] Theres not alot of reviews on that specific seasonic psu but heard that seasonic is the best PSU to go for so is this recommended or look for others?

[r.linder]

Yes, it's an ATX 3.0 PSU with a 12VHPWR cable

[Caldari Ghost]

check the amazon reviews, theres a ton.

[Tonepoet]

Well I mean yeah. Worst case scenario is that you want to use it with a 14900k.

According to corsair[www.corsair.com], the math goes something like this:

C.P.U. T.D.P.
G.P.U. T.D.P.
150 watts for components and peripherals
150 watts of unused overhead for efficiency and upgrades.

So 14900k 253 watts.+4080 320 watts+150+150=873

So it’s too weak, but you have to remember that overhead isn’t strictly necessary, and if we’re concerned about efficiency, it’s better to go with a better 80+ rating if your budget allows it. We can subtract 150 and see that we really should only strictly need 723 watts, and this is likely why nvidia themselves only recommend a 723 watt supply[www.nvidia.com].

Some people might try to argue that you should have overhead for excursions, but the power rating of a power supply is supposed to be for its sustained draw, and it should be able to handle brief excursions above its power rating.

This is especially true of A.T.X. 3.0 power supplies, since the A.T.X. 3.0 standard has certain excursion threshold requirements[edc.intel.com]. A power supply greater than 450 watts with a 12vhpwr connector must be able to handle 200% excursion for 100 nanoseconds, a 180% excursion for 1 milisecond, a 135% excursion for 10 miliseconds, a 110% excursion for 100 miliseconds and sustain load indefinitely.

Seasonic is one of the most trusted brands. They won’t advertise a power supply as an A.T.X. 3.0 model unless it is compliant with the standard. This is the main added feature of the A.T.X. 3.0 standard, alongside the 12vhpwr connector itself. However, considering that you can just use an adapter for 12vhpwr if you really need to do so, the excursion ratings are the main reason to buy such a power supply.

Techpowerup indicates that the RTX 4080 F.E.[www.techpowerup.com] has 20 milisecond excursions of up to 341 watts. That’s under 10% of the T.D.P., meaning the power supply should be able to handle such excursions for a sustained total of 100 miliseconds.

Moreover, Intel promises on their spec sheets that their processors won’t exceed excursions above maximum turbo power for more than 10 miliseconds (click the question mark) next to the Maximum Turbo Boost spec[www.intel.com] (I assume this means at stock clocks though).

Moreover, the worst I’ve heard is that the RTX 4090 spikes up to 600 watts. A 4080 isn’t a 4090, but it stands to reason that a more power hungry card would have worse spikes., so we’re looking at 250 watts max.


250 is about 78% of 320, which brings a 250 watt excursion beneath the 180% threshold, meaning the power supply should be able to handle that much for a millisecond in order to be A.T.X. 3.0 compliant, if we’re going by just the G.P.U’s. Contribution to the P.C’s.

Plus realistically speaking, you’re probably not using a 14900k. By the end of the month we’ll have Ryzen 9000 series C.P.U.s which top out at a 170 watt T.D.P., and even the 14700k only has a 219 watt T.D.P. The 7800x3D only has a T.D.P. of 120 watts.

However, the thing about P.S.Us. Is that the cost of overspeccing it isn’t necessarily very large and a power supply is one of those components you can potentially reuse for a very, very long time, esp. since the standards don’t change very often and the last change happened rather recently. If you have room in the budget, this is the component most worth overspeccing to future proof. Also, the risk of underspeccing your supply isn’t worth the few bucks you spend on a computer that, necessarily costs well over a thousand dollars by virtue of the G.P.U. alone.

It also needs to be noted that some board partners might advertise a higher T.D.P. than Nvidia, and it’d be better to go by the number given by your manufacturer since they likely applied a stock overclock that changes the T.D.P. of the product if they advertise a higher number.

But also, right now? I wouldn’t advise buying the Seasonic supply.

Why? Mostly just ‘cause I think the Super Flower Leadex III 850W[www.newegg.com] is a better deal right now. Newegg is offering a $15 off coupon code and a free Megacool case fan valued at $32. Superflower is at least as trusty as Seasonic, if not even more-so because they also offer O.E.M. rebadging for other companies. So you’re only spending $80 and getting a fan that’s likely comparable to the Noctua NF-A12x25 PWM for free.

Granted, you might be spending that $15 you save on the $17 SUPER FLOWER 600W PCIe 5.0 / Gen 5 12VHPWR PSU Cable[www.newegg.com] if you don’t want to use the 12vhpwr adapter that likely comes with your graphics card, but you’re still getting the fan.

It’s obstinately not an A.T.X. 3.0 supply, so excursions are more of a concern but the informal expectation is that a power supply should expected to handle excursions in excesss of its rated power by 30% for 10 miliseconds anyway. Even thermaltake’s supplies have been shown to handle a 135% excursion much by Gamer’s Nexus, and the enthusiast community loathes those. You’re still exceeding Nvidia’s recommendation for a 4080 based system by 100 watts, giving you a total 128 watts of headroom (based on reference spec.), even if corsair would try to upsell you to something rated for ≥900w.

But either way I think you’ll be fine though, and it would be understandable to prefer an A.T.X. 3.0 compatible system.