Why have a +600 Watt PSU in ITX Factor?

[Imbellis]

I was looking around and noticed that there are 800 watt PSUs in SFX-L form factor which got me wondering - why does anybody need an 800 watt PSU in an ITX Case? I brought this too a wattage calculator and got this:

This is the highest I could reasonably get in a non-water cooled ITX case without using a "stupid" cpu (9590) - though I'm sure I could squeeze 30 more watts - but most people wouldn't add 2 more HDDs and other similar things.

[minibois]

'cuz it's possible.

 

But uhhh, I got a 750W PSU while I would be just fine with a 550W PSU. I did this because that means my PSU can run fanless at all times (even at max load). Not sure if these SFX (I assume SFX?) PSU's can run without spinning the fan, but that is what I'm just gonna guess.

[Mira Yurizaki]

Most power supply calculators overestimate (sometimes grossly) what you really need. The few times I tried getting Outervision's PSU calculator to line up with what I observed couldn't match up with any of their settings. It was always too high.

 

Anyways, maybe some people want a smaller power supply in their larger cases. SFX can fit in ATX mounts with an adapter. There's also an X99 board in mini-ITX flavor if you really want it.

[manikyath]

because some people have very weird fetishes when it comes to overclocking, PSU headroom, and/or quiet operation.

[Damascus]

Ahh, here's the issue.  The 1800x isn't exactly a high power chip.  Try using a 7980XE and a vega 64 with anything but a high wattage PSU.  As a mattress of fact, the system I just mocked up would be more comfortable at 1000-1500 watts.

[Imbellis]

6 minutes ago, Damascus said:

Ahh, here's the issue.  The 1800x isn't exactly a high power chip.  Try using a 7980XE and a vega 64 with anything but a high wattage PSU.  As a mattress of fact, the system I just mocked up would be more comfortable at 1000-1500 watts.

Edited (with the 9590's 220 watt chip), it equals out to what the 7980XE and Vega would be; for the 7980 is rated at 50 watts under the 9590 and VEGA is 50 watts more than the Titan XP.

 

Excluding overclocking - that system is rated at 551 watts with a "safe PSU" of 601 watts.

 

Either way, with that CPU- a low profile cooler wouldn't fit in SFF Cases.

[Stefan Payne]

Because there is no sense in making a 550W Titanium PSU

And because you can.

[Damascus]

26 minutes ago, Imbellis said:

Edited (with the 9590's 220 watt chip), it equals out to what the 7980XE and Vega would be; for the 7980 is rated at 50 watts under the 9590 and VEGA is 50 watts more than the Titan XP.

 

Excluding overclocking - that system is rated at 551 watts with a "safe PSU" of 601 watts.

 

Either way, with that CPU- a low profile cooler wouldn't fit in SFF Cases.

Plenty of itx cases are capable of cooling that setup and even overclocking them, especially on a custom loop.

 

Also, an overclocked i9 can pull hundreds of watts.

 

On top of that, any high end gpu will actually draw in spike cycles - not a steady "300w" it'll go 50w, 600w 300w etc. all in a few secondscan if the psu has a 550W limit you are screwed, the protection will trip and it will shit down.

[Imbellis]

2 minutes ago, Damascus said:

Plenty of itx cases are capable of cooling that setup and even overclocking them, especially on a custom loop.

 

Also, an overclocked i9 can pull hundreds of watts.

 

On top of that, any high end gpu will actually draw in spike cycles - not a steady "300w" it'll go 50w, 600w 300w etc. all in a few secondscan if the psu has a 550W limit you are screwed, the protection will trip and it will shit down.

Yeah you're correct about the wattage of i9s pulling hundreds. I think I may've not been clear, but in the first post I specified not using water cooling - as that can add wattage and extreme SFF cases don't support it well.

 

As for the GPU's wattage variation - I didn't take that into account.

[Guest]

Totally agree.  600W tops.

 

Lots of ODM/OEM's ask me why Corsair doesn't do a 750W SFX as they show me their latest and greatest.  I tell them:  You don't need more than 600W for any build that can only accommodate one graphics card.  And even if you use the SFX PSU in a mid-size tower (something I'm surprised a lot of people do), the PSU isn't large enough to accommodate all of the connectors you would need to use that much power (unless you do a whole bunch of pig-tail connectors.  Four PCIe on a single cable anyone?  ;))

[Corsair Blake]

The actual reason is because there are cases that have been made this past 12 months which make the use of ATX motherboards with an SFX-L based PSU. It's something I would personally do if I was able to design a case.

 

If you look around, you'll find it.

 

 

[Guest]

Except the PSU doesn't have enough connectors.  ;-)

[Cookybiscuit]

PSU with higher wattage rating = it doesn't work as hard = quieter. My 1000W PSU pretty much never comes out of passive mode.

[PlayStation 2]

So you can use a Vega card.

[Patrick3D]

LinusTechTips actually covered PSU efficiency in a video last year.

tldw; Across the range of power supplies tested, the difference in power draw was only 25W between a 1500W and a 450W PSU.

 

[Quaker]

On 8/14/2017 at 3:26 PM, Cookybiscuit said:

PSU with higher wattage rating = it doesn't work as hard = quieter. My 1000W PSU pretty much never comes out of passive mode.

This is not entirely true. If your system is consuming say, 400watts, your 1000watt PSU needs to work just as hard as 550watt one does, to produce that 400watts. You can also get passively cooled, lower wattage, power supplies that are quiet all the time.

 

Unless you actually need 1000watts - which would basically mean a highly overclocked system with 3 or 4 way SLI/CFX - it is very un-economical price/performance-wise to get a 1000watt psu.

And before you talk about "efficiency" - you'll need to run your computer for a long, long time to recoup the added expense of a larger (or gold rated) power supply's extra initial cost.

 

In any case - in answer to the original poster - they make 800watt SFX PSUs because people will buy them. People buy them because they (mistakenly) think more watts is better. Given the current power draw of most ITX systems, very few people would ever need more than a 650watt power supply.

(I for example, am using a 650watt ATX power supply in my ITX build because I'm running an older, power hungry R9 390. If I was using a GTX-10xx, I'd need less).

 

(And yeah, I know, there's going to be someone who talks about their ITX system with an overclocked X99  system, etc, etc, or some special situation involving a custom build, but ... )

 

EDIT - My bad - I misread the original post as 800 watts instead of 600 watts. There are of course, many situations where you could use a 600watt SFX power supply. For example, building a system in a Node 202 case with an AMD Vega graphics card.

 

[Guest]

1 hour ago, Quaker said:

This is not entirely true. If your system is consuming say, 400watts, your 1000watt PSU needs to work just as hard as 550watt one does, to produce that 400watts. You can also get passively cooled, lower wattage, power supplies that are quiet all the time.

Actually Quacker, that's not always the case.

 

Higher wattage PSUs have more robust parts that allow them to output the higher wattages they're rated at.   They have higher temperature ratings, different de-rating curves (de-rate often starts at a much higher temperature) and while the parts may give off the same amount of heat in either PSU when operating "within spec", in a lot of cases the higher wattage PSU will have larger heatsinks that can dissipate the heat over a larger area requiring less active cooling.

 

The whole "fanless PSU" market is filled with 850W PSUs that are sold as only 600W (but cost as much as an 850W, unfortunately).

 

 

[System Error Message]

have you seen rx vega? that thing can consume 450W just for the card alone using +50% power setting.

[Stefan Payne]

Because +50% power consumption for 5-10% performance makes total sense...

[Exprima]

Just in case you wanna put an RX Vega 64 in your ITX build. :^)

[turkey3_scratch]

6 hours ago, System Error Message said:

have you seen rx vega? that thing can consume 450W just for the card alone using +50% power setting.

Hmm turned out bad for me.

[Herman Mcpootis]

21 minutes ago, turkey3_scratch said:

Hmm turned out bad for me.

so Vega can toast bread, boil water and heat up your house while you play crysis 3? sounds perfect, where can i get one?

[turkey3_scratch]

12 minutes ago, herman mcpootis said:

so Vega can toast bread, boil water and heat up your house while you play crysis 3? sounds perfect, where can i get one?

Just stick it in the toaster and it's good to go!

[System Error Message]

12 hours ago, Quaker said:

This is not entirely true. If your system is consuming say, 400watts, your 1000watt PSU needs to work just as hard as 550watt one does, to produce that 400watts. You can also get passively cooled, lower wattage, power supplies that are quiet all the time.

 

Unless you actually need 1000watts - which would basically mean a highly overclocked system with 3 or 4 way SLI/CFX - it is very un-economical price/performance-wise to get a 1000watt psu.

And before you talk about "efficiency" - you'll need to run your computer for a long, long time to recoup the added expense of a larger (or gold rated) power supply's extra initial cost.

 

In any case - in answer to the original poster - they make 800watt SFX PSUs because people will buy them. People buy them because they (mistakenly) think more watts is better. Given the current power draw of most ITX systems, very few people would ever need more than a 650watt power supply.

(I for example, am using a 650watt ATX power supply in my ITX build because I'm running an older, power hungry R9 390. If I was using a GTX-10xx, I'd need less).

 

(And yeah, I know, there's going to be someone who talks about their ITX system with an overclocked X99  system, etc, etc, or some special situation involving a custom build, but ... )

not so true. From the lower thermals the PSU isnt working as hard as a 550W does. At 400W the 1KW PSU is using 40% of its capacity while the 550W is using nearly 80%. Because of that the capacitors arent being strained as much and last longer. You get less thermals from switching because of the lower variance in DC voltages and the higher grade components used. So even at 400W usage the 1KW PSU will pull less from the wall than the 550W PSU and will be cooler too. So not only does this mean better efficiency through lower thermals but your PSU will last a lot longer especially the capacitors.

[Quaker]

7 hours ago, System Error Message said:

not so true. From the lower thermals the PSU isnt working as hard as a 550W does. At 400W the 1KW PSU is using 40% of its capacity while the 550W is using nearly 80%. Because of that the capacitors arent being strained as much and last longer. You get less thermals from switching because of the lower variance in DC voltages and the higher grade components used. So even at 400W usage the 1KW PSU will pull less from the wall than the 550W PSU and will be cooler too. So not only does this mean better efficiency through lower thermals but your PSU will last a lot longer especially the capacitors.

Lol! I can't help laughing at this.

 

1. Just because a power supply is rated at 1Kw does not guarantee that the components in it are any better "quality" than those in a 500watt supply. Many of the components are exactly the same - it's mostly just the actual current carrying components that are more highly rated.

2. While it's true that the 1Kw PSU would only be using 40% of it's capacity, at 400watts it's producing roughly the same amount of heat as a 500watt supply. The only difference in thermals would be the difference in efficiency between the two supplies when running at 400watts. It's quite possible that a 1Kw supply could actually use more power at 400 watts output, than a 500watt. depending upon the overall efficiency and design of the particular supply.

3. Differences in the temperature of any particular components does not negate the fact that you would be essentially creating the same amount of actual "heat". The heat doesn't disappear because you measure a lower temp - it's simply more diffused*.

4. At 400watts output an 80+ rated power supply would draw roughly 500 watts from the wall. The only difference would be the "actual" efficiency of the particular power supply at the 400watt level, which would only vary by a few percentage points. As above, the 1Kwatt could be 85% efficient at that output while some 500watt supply could be 86% or whatever.

5. The life of the capacitors would be determined by the quality of the capacitors and the heat/temperature of the capacitors themselves. In a higher rated power supply the capacitors would generally be "larger" - that is, have more microfarads - but they could be the same voltage and "quality" as in a lower wattage power supply. It's the voltage (and the power supplies ability to not exceed it), quality of construction, and localized temperature that most affects longevity.

 

* this also applies to CPUs and GPUs as well. When you lower the temperature of a CPU/GPU by increasing the cooling, you still have the same amount of heat being produced - it's just not localized at the chip as much. The same quantity of heat still goes into the surrounding atmosphere however - it doesn't magically disappear.