SFF PSU idea - why’s nobody done this?

[Harnser]

I am a quiet freak. I’m also keen on very small computers.

With every case I’ve sketched, it’s been the SFX PSU that’s increased the bulk the most - because it’s a shape that doesn’t complement the motherboard/graphics card. Which the Flex ATX design does. The EVGA Hadron Air tried this, but was let down by the noise of the PSU (and IMO the placement of the PSU next to the graphics card).

Given the problem with these 1U / Flex ATX power supplies is the noise, why not take a 1U power supply (semi-fanless preferably), remove the 40mm fan and put 2x92mm** thin fans on top, blowing air down onto the components and out where the 40mm fan was? By my calculations they’ll shift approx the same CFM (comparing 2x Noctua with a 500W 1U PSU - I forget which) and will be far, far quieter.

So, why’s no one produced this? Is there a flaw in cooling this way?

Here’s a diagram of what such a PSU would allow, with a mITX motherboard. The layout I’m thinking of is like the Hadron, but with the graphics card and PSU top & bottom, so both can use fresh air - or the PSU can exhaust internal air (as shown):

* If Gigabyte added heat pipes to their cooler and a larger fan (vs a solid block of aluminium) I reckon it’d make a world of difference. Shame really, as the card is sweet and connectivity excellent

** 92mm will fit in some 1U PSUs, the rest need 80mm. If I designed the housing I’d make a wider FlexATX PSU to allow 92mm fans to fit.

 

[Stevo_]

Pretty much a TFX supply, those are used by some like InWin, Dell, and others in SFF cases like this one though it only has one low-profile single slot. I think if power keeps dropping you'll see these more often.

 

[EdZ]

So, why’s no one produced this?

Basically because it's non-standard, and not close to any existing standards; totally the wrong airflow path to be placed where a 1U PSU would currently be, totally the wrong shape to be placed where an ATX or SFX PSU would currently be.
This means that the market for such a PSU would be tiny, limited only to cases designed to use it (which would effectively mean cases produced by whoever is producing the custom PSUs). To make that work, you need a lot of volume. OEM workstation manufacturers can manage this and many workstations end up with custom PSU designs, but if you're selling just a PSU it needs to actually fit in some cases.

 

[iFreilicht]

I actually modded a FlexATX PSU to do something quite similar with a single 80mm fan getting air directly from the outside, and to be honest, I believe that FlexATX PSUs are the future of SFF systems.

But as EdZ said, there is no standard for this, so the chance of seeing it fly is very low. BTW, there seem to be quieter 40mm fans, from what I've heard the scythe and noctua models are quite good.

 

[Harnser]

Pretty much a TFX supply, those are used by some like InWin, Dell, and others in SFF cases

Hi Stevo_, you're right it is like a TFX PSU, the main difference IMO being that Flex ATX units can be under 42mm thick, while TFX is specc'd at 63.5mm. Adding a thin fan on top brings them closer, but 1cm difference is important in SFF arrangements.

I think if power keeps dropping you'll see these more often.

Let's hope so My system draws under 200W at the plug under full load, and even with a GTX 970 a 400W PSU should cover it...

 

[Harnser]

Basically because it's non-standard, and not close to any existing standards; totally the wrong airflow path to be placed where a 1U PSU would currently be, totally the wrong shape to be placed where an ATX or SFX PSU would currently be.
This means that the market for such a PSU would be tiny, limited only to cases designed to use it (which would effectively mean cases produced by whoever is producing the custom PSUs).

Thanks EdZ, all sensible points! I take heart that there's nothing mechanically wrong with this design

 

[Phuncz]

BTW, there seem to be quieter 40mm fans, from what I've heard the scythe and noctua models are quite good.

Yeah they are quieter but they also have very little airflow and very low static pressure.

About FlexATX PSU's: at the moment we're still struggling with getting SFX to perform at a level mATX users are accustomed to (500-600W, quiet) and it maybe getting there with the SFX-L PSU from Silverstone but there is no one doing what they are doing. SFX needs more attention to mature and it's been many years already. I doubt FlexATX will have a chance anytime soon considering it is more of a OEM spec.

 

[Harnser]

About FlexATX PSU's: at the moment we're still struggling with getting SFX to perform at a level mATX users are accustomed to (500-600W, quiet)

How many current builds (assume nVidia Maxwell, Intel) need 500-600W, and how much is user expectation that a bigger power supply is better? I don't overclock, so I don't have a feel for how that changes power consumption.

 

[Phuncz]

While SFF doesn't need to have 500W per sé, you don't want to go near the max output of the PSU if noise is a concern. Since your concept is using quieter fans (most likely lower pressure & airflow) and recycling hot air from the GPU and CPU, it will need an amount of buffer to keep it quiet. If the purpose is to make a 1U PSU more silent, it might be possible but you can't just replace fans with quieter ones and expect the same performance.

We've seen this with the ST45SF-G where the fan-mod that replaces it with a much quieter fan, also lowers it's cooling performance. This also lowers it's voltage stability at the end of the power output and reduces it further when feeded with warm air.

But I don't see the advantage of this concept which will result in roughly a 12L case when there are already comparable cases that allow this with the SFX PSU's that are already on the market. Considering we (SFF community) already struggle with options in this area, another variant just seems very unlikely. Although not impossible, but don't expect any manufacturer to jump on this.

 

[iFreilicht]

While SFF doesn't need to have 500W per sé, you don't want to go near the max output of the PSU if noise is a concern. Since your concept is using quieter fans (most likely lower pressure & airflow) and recycling hot air from the GPU and CPU, it will need an amount of buffer to keep it quiet. If the purpose is to make a 1U PSU more silent, it might be possible but you can't just replace fans with quieter ones and expect the same performance.

We've seen this with the ST45SF-G where the fan-mod that replaces it with a much quieter fan, also lowers it's cooling performance. This also lowers it's voltage stability at the end of the power output and reduces it further when feeded with warm air.

But I don't see the advantage of this concept which will result in roughly a 12L case when there are already comparable cases that allow this with the SFX PSU's that are already on the market. Considering we (SFF community) already struggle with options in this area, another variant just seems very unlikely. Although not impossible, but don't expect any manufacturer to jump on this.

As you just explained, with better cooling comes more stable performance. Having a PSU with two 80mm or 92mm fans on a PSU would make it more silent and more reliable, especially when you're scratching on the maximum Wattage it can supply. With two fans, the cooling should have quite a bit of headroom.

Also, the form factor is just very interesting. SFX limits us to cases with a minimum height of about 65mm, while these AirFlow1U or AirFlowFlexATX form factors would enable cases of a heigh of 54mm (wen the fan(s) is/are 10mm thick), which can make a huge difference optically. Of course, if the case has a setup as shown in the OP, the difference would be negligible.

While we're at it, I really like the names AF1 and AFF for these form factors, maybe we should keep them to make this discussion a bit easier.

AF1 would be a 100(W)*50.5(H)*190+X(L) PSU with two 92mm fans in the top.
AFF would be a 81.5(W)* 50.5(H)*150+X(L) PSU with one or two 80mm fans in the top, depending on the size.

Anyway, you may be correct with your observation that manufacturers will probably not pick this up, there just aren't enough use cases as of now.

 

[Phuncz]

Also, the form factor is just very interesting. SFX limits us to cases with a minimum height of about 65mm, while these AirFlow1U or AirFlowFlexATX form factors would enable cases of a heigh of 54mm (wen the fan(s) is/are 10mm thick), which can make a huge difference optically. Of course, if the case has a setup as shown in the OP, the difference would be negligible.

While 54mm thickness might be nice, the PSU proposed is also twice as long, meaning you are losing a lot of volume just for 11mm less thickness overall. Also, at a certain point, you are nearing the point you can no longer find CPU coolers capable enough to quietly cool the popular high-end CPU's due to height (~35mm with fan for a 54mm thick case). And at this point when you are just lowering maximum supported hardware, that it becomes very close to just building a specific PC with custom components anyway.

 

[Necere]

Once the fans are factored in, it's really not much of a gain over SFX or TFX. What I do think would be interesting is a 1U/flexATX PSU with an ~80mm blower at the intake end in lieu of a 40mm fan. The challenge there would be leaving room for cables, but if that could be worked out, a 450W blower-cooled 1U PSU between 230-250mm long seems possible.

 

[Stevo_]

Hi Stevo_, you're right it is like a TFX PSU, the main difference IMO being that Flex ATX units can be under 42mm thick, while TFX is specc'd at 63.5mm. Adding a thin fan on top brings them closer, but 1cm difference is important in SFF arrangements.

Let's hope so My system draws under 200W at the plug under full load, and even with a GTX 970 a 400W PSU should cover it...

My main point was that the approach has not been completely ignored, though not in 1U. But I think you'll need to be thicker like TFX to balance the air openings for good flow while not making it obscenely long. An 80mm fan trying to blow thru a cramped 40mm high enclosure out thru a minimal area opening will likely make noise on its own just from the air rushing.

 

[CknSalad]

It would be awesome if external power bricks/power board solution could be cheaper and were mass-produced for the SFF market. 330w (Dell brick) is the highest, while it seems that the HD-Plex 250w is the most popular/accessible power-board to get. I know dondan has stated that in benchmarks this combo can handle up to 400w. However, I am wondering if anybody knows what is the most this combo can handle stability wise when gaming.

I feel like if this power combo was more accessible, we would be seeing a lot of nice 3-5L pc case builds if this becomes popular. As of now, this power solution makes a huge dent on SFF DIYers wallets as it is a good $100 or so more expensive vs. using an SFX/SFX-L psu.

 

[Zap]

Pretty much a TFX supply

My thoughts exactly.

These are 300-350W TFX PSUs that are 80 Plus Gold.
FSP300-60SGV
SeaSonic SS-300TGW
SeaSonic SS-350TGM

I'd imagine the 350W SeaSonic version could probably run a GTX 970 with a Haswell quadcore and a couple drives pretty easily, and the 300W version should be able to run a possible future GTX 960.

It would be awesome if external power bricks/power board solution could be cheaper and were mass-produced for the SFF market. 330w (Dell brick) is the highest, while it seems that the HD-Plex 250w is the most popular/accessible power-board to get.
...
I feel like if this power combo was more accessible, we would be seeing a lot of nice 3-5L pc case builds if this becomes popular.

Some of us consider the power supply to be an integral part of the volume of the PC. Otherwise, why not make a tiny box with power button, USB ports, audio ports and video ports for your desk, connected by an umbilical cord to a big "power brick" holding the actual computer? I can imagine a PC smaller than a NUC but with the "power brick" holding the CPU/mobo/GPU/drives. You're basically just moving part of the volume of the computer to another location.

 

[EdZ]

I'd imagine the 350W SeaSonic version could probably run a GTX 970 with a Haswell quadcore and a couple drives pretty easily, and the 300W version should be able to run a possible future GTX 960.

My 300W SFX happily handles a Sandy-Bridge Xeon and a 970 (with only one SSD), so 350W would easily be enough for the same plus some extra HDDs.

 

[Screes]

The only reason we even have good SFX PSU's is because Silverstone makes them for the cases it designs. If it wasn't for this, then SFX would be just as hard to find as TFX and other SFF PSU's.

So its not that SFX is "popular", its just that a single manufacturer started making cases that required them and then since no one was selling them started making them themselves.

So get a case manufacturer to start mass producing a SFF case that requires a TFX PSU that becomes really popular like the SG05 and you'll get more TFX PSU's on the market.

There's ways to make the SFX PSU's quiet. And nothing is to say that a different form factor is going to force a PSU manufacturer to put a quiet fan in it by default. It's a slightly different shape but the two are about the same size. And SFX is now allowing 120mm fans.. So I'd say SFX has the lead in the perfect dimensions argument now. Just barely big enough to fit a 120mm fan on top of.

 

[Harnser]

But I think you'll need to be thicker like TFX to balance the air openings for good flow while not making it obscenely long. An 80mm fan trying to blow thru a cramped 40mm high enclosure out thru a minimal area opening will likely make noise on its own just from the air rushing.

That's a fair point. I have been wondering with 2 fans the impact on flow (will they combine together, or fight each other?) and dead areas, particularly at the closed-off end of the PSU. Sadly I have no skills to simulate this!

 

[Harnser]

While SFF doesn't need to have 500W per sé, you don't want to go near the max output of the PSU if noise is a concern.

Agreed. My understanding is PSUs have two ratings, a passive and active cooling output, and to keep a PSU quiet you want to be closer to the passive end.

I see an output of 200-450W as more than adequate for most users, so downrating a PSU would not be an issue. Lower number for the marketing literature, but (as with digital cameras & megapixels) a cycle I hope will break in the next few years.

Since your concept is using quieter fans (most likely lower pressure & airflow) and recycling hot air from the GPU and CPU, it will need an amount of buffer to keep it quiet.

The fans I'd picked had a similar CFM - pressure I'm afraid I don't know.

Re recycling hot air from the GPU and CPU - if you flip the PSU the other way up it can draw in from outside the case. I drew it that way thinking that when the system is under load and the PSU fan turns on, you're going to need to dissipate warm air from inside the case so it can be used as an outflow too. Without testing I don't know which would work better.

But I don't see the advantage of this concept which will result in roughly a 12L case when there are already comparable cases that allow this with the SFX PSU's that are already on the market.

I understand, but looking at the cases available there aren't too many options if you don't want a cube. It's only a sketch to say "components fit within" - I would hope size can be reduced to a L2 with extra height or the Jonsbo V2 volume without the silly PSU position (which is what I aim to get round with a long thin psu), but unless I pick up some SketchUp skills I don't want to try fitting hard drives et al in my 2D drawing
Better to err on the side of caution than overpromise!

 

[Harnser]

While we're at it, I really like the names AF1 and AFF for these form factors, maybe we should keep them to make this discussion a bit easier.

AF1 would be a 100(W)*50.5(H)*190+X(L) PSU with two 92mm fans in the top.
AFF would be a 81.5(W)* 50.5(H)*150+X(L) PSU with one or two 80mm fans in the top, depending on the size.

I like - great work!