PSU tier list 2.0

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You do know that the ground wires in a 12v DC system carry 12v right? That's how the sense wires make the connection, they still see 12v, at a seriously low amperage, just enough to trip. JG is right about them being connected to ground, but they aren't themselves a ground wire as used by the pcb ground system, they are still sense wires that use the ground as part of a parallel circuit.
 


What I'm trying to say is that simple math shows that either the 6-pin or 8-pin PCIe cable wattage rating is faulty. All this talk of PCIe cables is indeed a lot of fun, but you have to at least agree with me that the 75W rating is silly.
 
The gpu sets the 75w draw, not the psu. In a 6pin, both 12v wires are connected inside the gpu. For all intents, it's seen as a single source. Because of the nature of electricity, when running multiple wiring to a single source, amperage is reduced by the amount of wires used. So 75w ÷ 2 = 37.5w per wire. The wire and psu is capable of @ 60w per 18ga at that length. So a 2x 12v in a 6pin is actually capable of 120w, but the psu sets the 75w limit. That's if the pcie are in fact 18ga, which some uber cheap psus don't use, they'll use 20ga which is only good for @4a or @50w. In the 3wire 8pin, you've generally got a wire capability of 180w, 60w x3 but the gpu sets a 150w draw limit. If you plug a 6pin pcie into a mobo (mine has that for pcie slot support) it'll draw more than 75w if needed, upto it's 120w limit or whatever the mobo sets it as. This also takes into consideration cable lengths. That 60w/5a @12v is only good for a certain length pcie. Once you add length like an extension, it starts lowering amperage capacity drastically. So if a normal pcie 12v length is good for 5a, having longer leads or using an extension can cut that back to @4.5a or 54w. In an 8pin, 54w x3 = only 162w so barely makes the 150w draw limit and a 6pin sees a drop from 120w max to 104w, still well above the 75w gpu setpoint. In that instance, a 2x 6pin gpu is superior to a 8pin gpu as the amperage/voltage tolerances have much greater cushioning.
 


I think you mean the GPU sets the limit 😉

But I think the ratings for cables should not be related to what GPUs limit; Since we both agree that the 6-pin PCIe cable is capable of more than 75W, I just think that the cable should be rated for more; even if every GPU on the planet limits its power on that cable to 75W, I think the cable itself should be rated separately since a GPU is not the sole application with which the cable can be used.

PSUs that use 20AWG, that's their fault; GPU manufacturers should not have to play around them not following the ATX spec, those unethical power supplies.

But now the whole topic has shifted anyway, don't know where we even began. But the entire 8-pin cable is a disaster, it's a shame money schemes got in the way of what could have been an actually seemingly good cable.
 
Well I have an 8 pin gpu, Asus 970. Many gpus in the past, especially amd, used dual 8pin connectors. Would be a pain to use 4x 6pin instead, so the 8pin isn't the disaster it looks like on paper and up until recent power efficiency levels and requirements in the latest gpus, it was an integral part of any higher wattage psu. If you can imagine a few years ago, a quad sli capable psu having upto 16x 6pin pcie connectors. Now try and make that a modular design. That would be a true disaster and the psu would be double let the size of ATX standard. Much easier to place 8x 6+2 wire sets.

As JG said, it may not work as those pencil pushing experts intended on paper, but the 8pin pcie works just fine as is.
 
I don't like the idea of going off gaming loads - games get tougher, people do video encoding, viruses appear that mine cryptocoins. Do you want to pass 450W when any of that happens?

Also, remember that the minor rails and the CPU are supplied via VRMs whose losses aren't included in your totals. Add another ~15% of those.

Charging cellphones from PCs is entirely possible, and likely to become more common again now that USB PD is taking off. Expect 25W+ if anyone plugs in a USB 3.1 card.
 


I would like to see proof of this. ~15% is way too much.
 
This ST application note is tailored to CPU VRMs, and from 2012. Fairly recent, and efficiency isn't likely to have improved that significantly since then unless people are moving to GaN FETs - I don't think they are yet. Reducing output voltage also harms efficiency.

Peak was around 86%, falling off to ~80 percent at full load. 1/0.8 = 1.25 (25% more input than output), so I was actually being too cautious.

The 12V > 5V/3.3V converters are likely to be more efficient - the high output current and low voltage reduces the efficiency quite a bit. >90% (11% more input) is reasonable there. But there's a lot more load on the CPU.
 


The VRM losses are included, that's what the motherboard power (part of it) is. Just like how graphics card consumption is not just the GPU, it includes the waste heat from the VRMs on the card.

The minor rails are practically not even used these days. 3.3V rail, memory, very small amount of power; if I'm correct Pascal GPus don't even use this rail anymore. 5V rail, hard drives, PCI, and I can't think of anything else.

Technically speaking, the "450W" in a 450W power supply means that a power supply loaded to that value, at the rated temperature, constantly, should last the warranty period. Anything else and "450W" is a meaningless number. It doesn't mean max power. Not true at all. It doesn't mean max continuous power. Not true either. So, really, it's just a dumb number on a label IMO; I don't believe power supplies should be rated by wattage. I think the rating of a power supply should merely be a load table where the amperage values are actually set to the OCP triggering point. That would actually be a sensible standard. Because it's already really stupid that power supplies, for instance, are rated for "20A" but OCP kicks in at 28A. It's extremely stupid I think, and while that leeway is there to account for transients, I still believe there needs to be more standardization. I don't think there's any reason to look at rated amperages at all honestly. There's no consistency with them.

The problem is I can't figure out what a 450W power supply is. Or what a 550W power supply is. It's easy to speak in terms of these wattages but there is still no clear definition on what they mean; no standard by which they are decided. Its a thing I've been trying to figure out for a long time by now: what rated wattage really means. Pretty much, until someone gives me a definition that can be proven to be consistent and true, I'll stand by my belief that it is just dumb.
 
^ The problem is the average consumer wants an easier decision.

Very few consumers would want to look at amps, rails protections, use power supply calculators online, and other such things. They want to look at a graphics card and see that it recommends a 500w power supply, then they go and buy a power supply from a brand they recognize. Throw in some Bronze and Gold ratings for flavor and that's about the extent of it. The manufacturers and sellers know the enthusiasts will go and find the information they want anyway regardless of what they write on the box, so why bother confusing the average customer?
 
Well you know discussing this stuff is great. If people don't discuss things, if they don't voice their opinions, nothing ever changes, nothing ever gets done. I think discussion is the number one thing that leads to communal knowledge. I do not get irritated at you all even if your opinion differs than mine; I am very radical when it comes to power supplies, but still appreciate hearing both sides of the discussions always. 😀
 
OK, this should spark some sniping...

I need a recommendation for a PSU. This will be to power a whole house firewall box. G3258 CPU on a micro (or itx) board, no GPU, a single SSD.

Req's:
450watt or smaller
Smaller box is better
Pref modular or semi, but not required.
Brand or color - irrelevant
Quiet is better. Fanless gets extra points.
Price? weeelllllll.....Anything over $100 is right out. Pref under $60.


Which one, and why.
 
Depends on how small you want to go. If you want to go with something console sized, like a Silverstone RVZ01B, then a SFX PSU, from Silverstone, or Corsair, are probably your best quality options. http://pcpartpicker.com/products/compare/Dv38TW,vrH48d/

If you are looking at a cube, or tower type case, a Seasonic 450w gold is probably your best quality option, followed by the new corsair CX450m. Personally, I would go with Seasonic, as the price isn't much more. You really cannot go wrong with Seasonic's gold rated units.

http://pcpartpicker.com/products/compare/FQ648d,xVkD4D/

 


Should have mentioned earlier...this will be going into a smallish custom case with a whole nother PC.
So 2 PC's in one physical box. The other is the HTPC/house server system.
 


So ATX form factor? If so, and if you wouldn't mind a 550W unit, the CX550M is under $40 ($20 rebate off $60 + 10% promo code) http://www.newegg.com/Product/Product.aspx?Item=N82E16817139147

But my recommendation is usually the FSP Hydro X 450 http://www.newegg.com/Product/Product.aspx?Item=9SIABP94H47003&cm_re=hydro_x_450-_-17-104-229-_-Product

Reason being this is the second most efficient power supply under low loads. Review: http://www.tomshardware.com/reviews/fsp-hydro-x-450-power-supply,4495.html

The only thing the Hydro X 450 does not fulfill is having modular cables, so I guess that's the downside and where the CX would win.
 


hmm....do I cheap out, or do I go all in and get 2 fanless's for the 2 systems in this "custom case that shall not be mentioned until it appears"...
I could almost do this fully fanless/no moving parts. Maybe 1 x exhaust fan.
grrr...and the 2 x CPU fans. Could fanless those as well.

The current HTPC PSU is an Antec VP-450, now 3-4 yrs old. Probably needs replacing anyway.

This could get interesting. And expensive.
 
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