Power Supply Gold PSU vs AC/DC PSU PICO - for durability, reliability and performance.

[dljonsson]

* I'm wondering what observations, experiences and technical facts others here
in this forum have about the question...

...Are AC/DC PSU/PICO solutions any match to the durability, reliability and performance
compared to gold modular SFX PSUs?

 

[Choidebu]

This is a hard question for me because IMO one chooses 'splitting" ac-atx into ac-dc + dc-atx due to size or shape constraints, which in turn means:

1. They are limited in maximum power available to them, i.e, only early this year that proper >330W, more affordable brick or internal solutions shows up. More common and economical dc-dc solutions were limited to 200W.

2. They are most often than not, being run close to their limits. So one would choose their psu first then choose the components within that psu's limit. Contrast this to what happen when you use atx/sfx solution: you pick your component then pick the psu wattage that you need which have leeway. Rating them at 50% load is also the norm, since it means the psu will run at max efficiency.

These two reasons would make the two comparison unfair, akin to comparing a city car used to carry a family of 4 to an suv carrying 6 for example. Which one will last longer (durability)? Which one is more comfortable (reliability)? Which one is more fuel efficient (efficiency)?

Efficiency wise, I'd say not that much different. Of course it'd go down the closer to limit with ac/dc bricks, but it'd also go down on idle with atx/sfx.

Durability and reliability will sure suffer when you drive a psu to its limits. So can't say much on these two...

 

[dljonsson]

Thanks for your clear answer.

With 105W CPU and a 105W GPU then in my current upgrade path it seems to me I'm clearly out of the AC-DC > PICO league. I'll likely need a 550 to 600watt SFX for sufficient headroom.

Once I get past this build though, I'll likely be looking further into what can be done within 200W-300w for a more
portable rig.

As more efficient and powerful GPUs and CPUs arrive on the market in upcoming years it will be interesting to see how SFF builds evolve. Even now I wonder how SFF builders over the last 5 years have seen things improve, even if it looks like Moore's law isn't as exact as it used to be.

 

[smitty2k1]

Thanks for your clear answer.

With 105W CPU and a 105W GPU then in my current upgrade path it seems to me I'm clearly out of the AC-DC > PICO league. I'll likely need a 550 to 600watt SFX for sufficient headroom.

Once I get past this build though, I'll likely be looking further into what can be done within 200W-300w for a more
portable rig.

As more efficient and powerful GPUs and CPUs arrive on the market in upcoming years it will be interesting to see how SFF builds evolve. Even now I wonder how SFF builders over the last 5 years have seen things improve, even if it looks like Moore's law isn't as exact as it used to be.

I think what really got the SSF game started was the NCASE M1 release in 2013.

 

[dljonsson]

Still wondering how Moore's law may or may not impact SFF technology in the near future.

Can we see smaller/more powerful - more energy efficient GPUs and CPUs being a game changer in the near future?

 

[Thehack]

I'd like to clear up some misconceptions:

1. Industrial power supply are just as good of quality as regular atx psu. If you consider sourcing from reputable manufacturers then it's the same as choosing a good quality atx platform. They are usually about equivalent to a gold rated.

2. The 50% load rating recommendation is a leftover of older switching technologies. There is only a 1-3% penalty going from 50% to 100%. If you use 240V like Europe, there is no penalty even, due to lower losses.

3. Currently the upper limit on separate AC-DC and DC-DC solution is 400w. Sufficient headroom is considered to be about 30%. So more or so a 300w-330w build. The issue with headroom is that this is due to transient power draw. Some GPUs are more prone to high current draw than others. Some of this can be offset by bulk capacitance into the power design of the DC-DC or power tuning. You really don't know since every new generation behaves differently. The acdc themselves also have overcurrent rating so it is really a muddy area of what you can get away with. For example the UHP series has a 150% overcurrent rating if properly cooled, so in theory you do not need headroom.

4. Some of the dissatisfaction with sfx comes with its form factor. The 125x100x63 doesn't compliment of our components.

5. What really hurts dcdc adoption is certification and high costs. Atx psu are churned out in thousands, all based on a similar platform then customized by brands. A certification would cost 10-15k and thousands per year to update and maintain it. I can definitely do a 400w customized unit but it'd take a huge kickstarter to do it. Then there are unforeseen risks and delays that plague those projects which hurts your brand in the long term.

 

[Windfall]

Thanks for your clear answer.

With 105W CPU and a 105W GPU then in my current upgrade path it seems to me I'm clearly out of the AC-DC > PICO league. I'll likely need a 550 to 600watt SFX for sufficient headroom.

Once I get past this build though, I'll likely be looking further into what can be done within 200W-300w for a more
portable rig.

As more efficient and powerful GPUs and CPUs arrive on the market in upcoming years it will be interesting to see how SFF builds evolve. Even now I wonder how SFF builders over the last 5 years have seen things improve, even if it looks like Moore's law isn't as exact as it used to be.

No, you don't need 500-600 watts. That's plain wrong. Dell 330W+HDPlex 400W AC-DC is going to be more than enough.

 

[duynguyenle]

I agree with Thehack on this. The argument of 'choosing a PSU that has 2x the power rating of your maximum typical load just so your PSU can run at max efficiency' is a total fallacy.

Let's consider a system with 'maximum expected load' of around 500W (say, a highly overclocked 8700K coupled with a highly overclocked 1080Ti, both concurrently running a power-virus type workload like Prime95 + Furmark).

Let's say you power said system with a 550W 80+ Gold PSU (a little close for comfort but let's go with this for the sake of argument). At full tilt, the PSU is going to be operating at 90% of its rated max continuous output. At this level, a 80+ Gold PSU provides 87% efficiency, pulling 574W from the wall.

Now let's assume you buy a 1000W Gold PSU just so your power supply operates at the top of its efficiency curve, at the same 500W power demand, the PSU is working at 90% efficiency, pulling 556W from the wall. The difference in efficiency rating is 3%, for a difference in power draw at the wall of 18W. Which basically is fuck all difference for all practical purposes.

Size your PSU appropriate for the load you're expected to pull based on your components, and don't rely on the 'TDP' manufacturers tell you, see if you can seek out some real world results from a reputable site (for example, Intel will happily tell you that the 8700K is a '95W' CPU but running all cores at 5.0GHz doing an AVX workload will see that CPU happily eating over 200W assuming you've got adequate thermal headroom).

If you know what your hardware demands are in real world situations, it's unnecessary to have 100% headroom in your PSU, it's a waste of good money that you could put towards other components.

Just my 2p.