Modding the ATX Cable

[Marv21]

Hello Guys,

iam absolut interresed in SFF Cases. I especially like the new Freilite Brevis S. I hope that the next Gen of GPU the strong GPUs will fit in it. So i have a carry around gaming PC ( VR / LAN).
But now my question, i didnt find it here already.
Everbody has to get this heavy chunky ATX Mainboard Cable to the Mainboard.
Is it possible to shrink it?
We have:
8 times Mass
5x +5VDC
4 times +3,3VDC
2x 12 VDC
1x -12VDC
1x PS_ON
1x -5VDC
1x 5VSB
1x Power OK.

Can we not just combine them in 9 Cables? How much Ampere are there flowing? I dont think that much.
Or is this a stupid idea? Not worth it?

 

[iFreilicht]

I'm pretty sure we talked about this in a different thread and yes, a smaller connector would be great. In theory, we could reduce the number of cables or use separate connectors so boards that need little power only need few connectors and boards that need a lot of power can still get it from the PSU directly. Some E-ATX mainboards already have a PEG connector to supply 12V to all their PCIe slots.
You could also eliminate 3.3V power completely and just generate that on the motherboard from 5V as 3.3V are needed less and less often. (Even SATA has dropped support for 3.3V by now)
BTW, -5VDC is not part of the standard anymore, and I could see -12V dropping in the future. Some PSUs don't even supply -12V anymore.
At that point, we'd be down to just 6 cables.

Thin mITX boards have already gotten down to only two cables (19V+ and Ground), but they can't turn the PSU off and only support processors with a TDP of 65W or less.

In theory, the pins of the connectors can carry quite a bit of power, they're rated for 9A, so that would be 108W for the 12V and 45W for the 5V rail, but the ATX and PCIe specifications are very careful, the connector is only allowed half the load it is actually rated for.

The real problem with this is that ATX12V ist a standard that every consumer mainboard supports. If you were to release a mainboard with a reduced connector, it would probably be DOA. Maybe you could get around that by including an adaptor, though that would kind of defeat the point of the exercise. Before something like this can happen, we first need a standard that is signed by all important players of the industry so new PSUs and Mainboards can use that connector and be compatible with each other. Just the chances of that happening alone are close to zero in my book.

What you could do if you just can't fit an ATX12V cable in your build, is to remove all extraneous cables from the ATX connector, as all grouped pins are usually connected together directly. So just leave out all 3.3V wires except for the one on pin 13, leave out -12V, leave out most 5V pins and maybe one 12V pin and all unnecessary ground pins. The connector will have the same size but at least the cable will be less thick.

 

[confusis]

An easy option here would be a PicoPSU - two wires! Some careful wiring and design (to power drives, 4/8 pin CPU connector, any gpu connector) and it would really simplify the design.

 

[EdZ]

Changing the motherboard standard wouldn't be too bad, an adapter cable would add to the BoM by $1/$2 in bulk, but it would be functionally compatible with existing PSUs. Changing the PSU-side connector is a bigger problem, because while even with an adapter it would mostly work, as soon as someone plugs it into a board that DOES still use lots of 3.3V or -12V for some board-specific weirdness then that's a world of headaches.

Sadly, SFX was probably the best time when this could have occurred, as it would make a nice break in nomenclature. Trying to explain "yeah, the form factor is SFX/ATX but the power supply isn't actually SFX/ATX but it will work with you ATX board probably maybe usually" isn't a great situation to be in.

 

[Marv21]

Hmm, i thought of a little adapter with bridges soldert around the pins. So yeah its custom and i would cut of the unnecessery cables from the PSU. Hmm.