Theoretical: repurposing PCI-E for EPS or doubling EPS 8-pin on a single-rail PSU

LePhuronn · 20 Nov 2018 at 14:23

Hi there.

This is a purely theoretical question to satisfy a curiosity I have for a pie-in-the sky modding project. The situation is this: I'd be looking to use the Maximus XI Gene motherboard which has 2 8-pin EPS connectors, and a RTX 2080 with its 8+6 pin PCI-E. Due to reworking some of the case internals, I'd be looking at either the Silverstone SX700-LPT or SX800-LTI SFX-L PSUs. Both of these are single-rail design, have a pair 8+6 PCI-E connectors for 2 GPUs, but only 1 8-pin EPS.

Since single-rail PSUs have their protective circuitry monitoring the total load on the PSU, in theory does it matter what 12V power is being delivered to where? Everything drawing 12V is monitored as a single thing, so if the PSU can drive 2 GPUs and a single EPS, would it be a lesser load to drive 1 GPU and 2 EPS?

So...

Question 1: could I rewire an 8-pin PCI-E into an 8-pin EPS? I'd need two double wires to populate the additional 12V and ground wires.

Question 2: could I double up all 8 wires out of the EPS into 2 connectors?

Hit me up with your thoughts, cheers.

lee32uk · 20 Nov 2018 at 15:26

That board can run fine with 1 x 8 pin EPS connected. If you were doing serious LN2 overclocking like 8Pack or der8auer etc then you would use both.

So a 2080 and i7/i9 etc will be fine on a good quality psu.

LePhuronn · 20 Nov 2018 at 15:41

Cheers. I which case then I'd probably make a dummy 8-pin to fill the 2nd connector purely for aesthetics.

Armageus · 20 Nov 2018 at 15:42

Cheap enough that you don't need to make one

My basket at Overclockers UK:

1 x Akasa PCI-E to ATX12V Cable Adapter (AK-CB051)= £2.39

Total: £5.13 (includes shipping: £2.74)

LePhuronn · 20 Nov 2018 at 15:46

But where's the fun in using somebody else's stuff?

plus it'd have to be sleeved and whatnot. Still, its very existence confirms the viability of question 1.

Thanks Armageus.

lee32uk · 20 Nov 2018 at 16:02

LePhuronn said:
But where's the fun in using somebody else's stuff? plus it'd have to be sleeved and whatnot. Still, its very existence confirms the viability of question 1.

Thanks Armageus.

I take it you don't have the psu yet ? Are you limited to SFX ones ? As there are units that come with 2 x 8 Pin EPS i.e Corsair RMx 750W but it is an ATX size unit.

LePhuronn · 20 Nov 2018 at 16:06

I don't have any kit yet. This project will probably never happen, but I'm making plans and working out what I can and cannot do. Given what I'll be doing to the case, there won't be any room for a full ATX PSU. Also, if anything ever happens I may not use the Gene anyway. But like I said I'm in the planning stages for a what-if and working things out based on my "like to have".