Discussion PCI-E x4 power delivery

jakejm79

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Mar 22, 2021
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My current build ~4L (9600K large cooler, 1650LP and 250W open frame AC-DC 12V PSU powering EPS directly) is a little on the bulky size and I was thinking about downsizing it.

Came across a video of the NUC 11 Pro boards (1135G7) and it seems to offer similar performance to my 9600K (at least in stock form) for a significantly smaller form factor and power draw and also can be powered by 12V rather than needing 19V like the older models.

After some quick measurements, a 1650 LP (laid on its back), a 3x2 PSU and a NUC board all make a pretty nice 7"x7" square and with a uniform height of around 1.5-2" (or about 1.5L).

But the NUC lacks a PCI-E slot, but does have 2 M.2 slots, one of which offer 4 lanes.

Now for the question, if I wire up a m.2 to open ended x4 slot will I be fine supplying the up to 75W to the 1650 over a x4 slot, I know x4 is normally limited (on motherboard) to 25W, but since 12V will be supplied direct from the PSU to the adapter board and not via motherboard traces will I be safe? Or is it a case of 1/4 the number of pins in the slot being the limiting factor.

Bonus question, I see the m.2 to PCIe adapters have power input for both 12V and 5V (red and yellow wires on the pigtail), from what I understand PCIe slots only provide +12V and +3.3V, there doesn't appear to be any real components on the adapter boards, my assumption is that the 3.3V signals are passed over the cable from the m.2 slot and only the 12V is injected in via the adapter, but the 5V wiring is there on the pigtail since they just use an off the shelf SATA (or Molex) to FDD adapter, does that sound correct?
 

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Shrink Ray Wielder
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My current build ~4L (9600K large cooler, 1650LP and 250W open frame AC-DC 12V PSU powering EPS directly) is a little on the bulky size and I was thinking about downsizing it.

Came across a video of the NUC 11 Pro boards (1135G7) and it seems to offer similar performance to my 9600K (at least in stock form) for a significantly smaller form factor and power draw and also can be powered by 12V rather than needing 19V like the older models.

After some quick measurements, a 1650 LP (laid on its back), a 3x2 PSU and a NUC board all make a pretty nice 7"x7" square and with a uniform height of around 1.5-2" (or about 1.5L).

But the NUC lacks a PCI-E slot, but does have 2 M.2 slots, one of which offer 4 lanes.

Now for the question, if I wire up a m.2 to open ended x4 slot will I be fine supplying the up to 75W to the 1650 over a x4 slot, I know x4 is normally limited (on motherboard) to 25W, but since 12V will be supplied direct from the PSU to the adapter board and not via motherboard traces will I be safe? Or is it a case of 1/4 the number of pins in the slot being the limiting factor.

Bonus question, I see the m.2 to PCIe adapters have power input for both 12V and 5V (red and yellow wires on the pigtail), from what I understand PCIe slots only provide +12V and +3.3V, there doesn't appear to be any real components on the adapter boards, my assumption is that the 3.3V signals are passed over the cable from the m.2 slot and only the 12V is injected in via the adapter, but the 5V wiring is there on the pigtail since they just use an off the shelf SATA (or Molex) to FDD adapter, does that sound correct?

this might help:

 
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jakejm79

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Mar 22, 2021
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this might help:

Thanks, that is helpful, it answers the 12V vs. 3.3/5V question.
The 4x vs. 16x is no longer an issue, found a 16x riser that will add no more bulk to the build.

So my follow up question is now about leaving the riser cable (and GPU) receiving 12V even with the NUC off. In that link it looked like he used a PSU with remote on, but since my PSU will also be powering the NUC that isn't possible, at least not without some additional workarounds with power on and gracefully shutting down (via power button) the PC.

Any real issues with leaving the GPU powered with the rest of the computer shut off? I suppose at worst the fans would continue to spin, but my 1650 is deshrouded and I plan to power the fans externally (to save what little power I can for the already power limited GPU). TBH its likely mostly a non issue since I will leave the computer on 24/7 and just have it sleep while idle.

Oh and one more bonus question, anybody help me source a NUC 11 board :-)
 

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Shrink Ray Wielder
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Apr 2, 2020
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Thanks, that is helpful, it answers the 12V vs. 3.3/5V question.
The 4x vs. 16x is no longer an issue, found a 16x riser that will add no more bulk to the build.

So my follow up question is now about leaving the riser cable (and GPU) receiving 12V even with the NUC off. In that link it looked like he used a PSU with remote on, but since my PSU will also be powering the NUC that isn't possible, at least not without some additional workarounds with power on and gracefully shutting down (via power button) the PC.

Any real issues with leaving the GPU powered with the rest of the computer shut off? I suppose at worst the fans would continue to spin, but my 1650 is deshrouded and I plan to power the fans externally (to save what little power I can for the already power limited GPU). TBH its likely mostly a non issue since I will leave the computer on 24/7 and just have it sleep while idle.

Oh and one more bonus question, anybody help me source a NUC 11 board :-)

For the "always on" issue I also have a solution:


Even could help you with a NUC11TNKi5

I bought one for testing my NUC1 eGPU but currently I have too many PC stuff laying around... if you would like to have it for your project just let me know.

 

jakejm79

Average Stuffer
Original poster
Mar 22, 2021
67
56
For the "always on" issue I also have a solution:


Even could help you with a NUC11TNKi5

I bought one for testing my NUC1 eGPU but currently I have too many PC stuff laying around... if you would like to have it for your project just let me know.

Thanks, I sent you a PM.