Discussion 12V eGPU musings

ygrt

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I want to build a small external GPU with integrated power supply. It'll be based on the ADT-Link R43ML, which is a PCIE to M.2 extender, and the Jeyi ThunderDock, a Thunderbolt 3 to M.2/NVMe case. The GPU I will use is a PNY GTX 1660 Super, which draws 125W, but I'd like to leave a bit of headroom and be able to accommodate an undervolted RTX 3060 at ~190W some day. The ADT-Link has a Floppy connector, the GPU an 8 pin PCIE connector.

I'm still undecided about the power supply, but as mentioned, I want it to be internal to minimise the total footprint.

I don't have a case yet, but I'd like for the build to be no thicker than 5 cm (2 in), which narrows down the possibilities for a PSU. As the title indicates, I'm considering the 12V route rather than using a full ATX PSU. The standard solution seems to be Meanwell's EPP or RPS series. Here's where I'm at with my considerations:
  • At the 2x4 inch form factor the EPP-200-12 can supply 140W without active cooling, and up to 200W with a fan. That would be sufficient, but according to Meanwell the fan should be installed 5cm away from the long side, effectively more than doubling the width. I'm toying with the idea of installing a small fan at the head side of the PSU, but I'm not sure it'd allow me to pull 190W?
  • The RPS/EPP 200 don't seem to have a PS_ON function. I don't want the GPU to be running constantly, and I'm not sure it'd be safe (for me, the hardware) to have a manual switch on the AC side?
  • The 300 series supplies up to 200W with convection-only cooling, so that's plenty, but they're also a full inch wider! One question remains: Where should the PS_ON signal come from? Maybe a USB port on the Jeyi could work...?
  • Cincon makes a 2x4 form factor PSU supplying up to 220W with convection cooling, the CFM260S120C. This could be a good alternative to the EPP-200, but I found no reference to its use in SFF projects. Why? Is it inferior to the Meanwell EPP in any way?
Please share your thoughts.
 

smitty2k1

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I can only speak to your first bullet about the Meanwell 200w unit. I had mine absolute crammed in my old Realan e-i7 case with no direct fan attached to it powering a 65w CPU and 75w GPU and had no issues. There were some case fans but the Meanwell was attached to a solid wall of the case.

Here are some photos:

 
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I want to build a small external GPU with integrated power supply. It'll be based on the ADT-Link R43ML, which is a PCIE to M.2 extender, and the Jeyi ThunderDock, a Thunderbolt 3 to M.2/NVMe case. The GPU I will use is a PNY GTX 1660 Super, which draws 125W, but I'd like to leave a bit of headroom and be able to accommodate an undervolted RTX 3060 at ~190W some day. The ADT-Link has a Floppy connector, the GPU an 8 pin PCIE connector.

I'm still undecided about the power supply, but as mentioned, I want it to be internal to minimise the total footprint.

I don't have a case yet, but I'd like for the build to be no thicker than 5 cm (2 in), which narrows down the possibilities for a PSU. As the title indicates, I'm considering the 12V route rather than using a full ATX PSU. The standard solution seems to be Meanwell's EPP or RPS series. Here's where I'm at with my considerations:
  • At the 2x4 inch form factor the EPP-200-12 can supply 140W without active cooling, and up to 200W with a fan. That would be sufficient, but according to Meanwell the fan should be installed 5cm away from the long side, effectively more than doubling the width. I'm toying with the idea of installing a small fan at the head side of the PSU, but I'm not sure it'd allow me to pull 190W?
  • The RPS/EPP 200 don't seem to have a PS_ON function. I don't want the GPU to be running constantly, and I'm not sure it'd be safe (for me, the hardware) to have a manual switch on the AC side?
  • The 300 series supplies up to 200W with convection-only cooling, so that's plenty, but they're also a full inch wider! One question remains: Where should the PS_ON signal come from? Maybe a USB port on the Jeyi could work...?
  • Cincon makes a 2x4 form factor PSU supplying up to 220W with convection cooling, the CFM260S120C. This could be a good alternative to the EPP-200, but I found no reference to its use in SFF projects. Why? Is it inferior to the Meanwell EPP in any way?
Please share your thoughts.

You can use the RPS200 if you put a slim 60 or 80 mm fan on top. If you choose another one, just make sure the PSU stays within ATX ripple specs.

For the power- ON/OFF issue, maybe my GxR-DIY could help.

The ADT riser should have a solder spot for 3.3V which you can use to trigger the GxR-DIY (this works fine for Mini PCs like the NUC, but I haven't tested it with the Jeyi Thunderbolt adapter yet)

 
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ygrt

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I can only speak to your first bullet about the Meanwell 200w unit. I had mine absolute crammed in my old Realan e-i7 case with no direct fan attached to it powering a 65w CPU and 75w GPU and had no issues. There were some case fans but the Meanwell was attached to a solid wall of the case.

Here are some photos:

That's a very neat build, thanks for sharing the album. With 65W CPU + 75W GPU you'd exactly hit the 140W under convection cooling the RPS is rated for. How much was the total system consumption? Some 10 or 20W above that?
Regarding the lack of PS_ON: I guess the PSU was simply always on and the DC/DC pico PSU regulated the power?

@REVOCCASES I'm hoping to bastardize a thin mini ITX case like the SuperMicro SuperChassis 101S for the project and stay below 50 mm for a total volume of < 2L. The encased RPS-200-12-C is already 40 mm tall ; what's the thinnest a fan can get?

Width is also a concern, as most thin itx cases are at most 200mm wide, and my GPU already takes up 126 mm + the 8 pin PCIE power connector. The encased RPS-200 is 62 mm broad, leaving only about 1 cm of space for the power connector on one side of the card and the riser board on the other.

The aforementioned Cincon CFM260 is rated at 1% ripple&noise, which would be within spec. According to the datasheet (https://www.trustedparts.com/en/part/cincon/CFM260S120) the encased variant is rated for 220W, while the open frame variant is rated for 140W.

A different route may be to go with a Meanwell UHP-200-12 (https://www.mouser.co.uk/ProductDetail/MEAN-WELL/UHP-200-12/?qs=YCa/AAYMW02wbY6zs%2B73Lg==), a passively cooled PSU rated for 200W. Another advantage is that it is only 54 mm wide. On the other hand, it is 194 mm long, which will be very hard to fit into those sub 200 mm cases, and it has a ripple rating of 240 mV, exceeding the ATX norm. Maybe something could be done about that though?

Thanks for the pointer to the GxR-DIY, I've been thinking about using it indeed, but I was unable to tell if it'd work with the ADT-Link riser (cf. R43-ML at http://www.adt.link/product/R43M.html). Where would you attach it?
 

ygrt

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Sorry for the brain dump, but I've been researching this for a while and hit a few dead ends where my judgement has reached its limits. In particular the Cincon looks almost too good to be true compared to the RPS-200, but I'm afraid it'll fry my GPU and burn my house down because there's something in the spec sheet I missed. I'd appreciate a comment on that matter!

Is there anything wrong with just using a line switch at the AC plug to turn the PSU on and off? No PSU with less than 75 mm width seems to support PS_ON. Otherwise it should somehow be possible to control the DC side via the GxR-DIY or something similar. Does the GxR-DIY conditionally interrupt the 12V depending on say the PCIE header of the riser, or is it used to control the PS_ON signal on a PSU that has that functionality?

A slightly wider case, say 240 x 200 x 45 mm would probably solve all my issues because I could just go with a RPS-400-12 and call it a day, but I haven't found anything of the sort. Do they exist?

...and sorry for the double post; I can't seem to edit my previous post.
 

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The Cincon looks good indeed. But better double check the datasheet, especially the de-rating curves. If you live in an 110VAC country, seems it only gives you about 180W output.

GxR-DIY can be used with any PSU, no need for PSon function. It acts similar like a relay.

But you need to get a trigger signal (+3V or more) from somewhere to switch it. if you would use one of below riser cables you could probably get that signal from the 3.3V pin on the riser (if the 3.3V lane is hooked up internally on the Jeyi, I haven't tried that):


The riser you chose doesn't have that pin.

Concerning the ripple: I would try to stay within ATX specs. Higher ripple will cause more stress on your GPU VRMs and can cause issues...
 
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ermac318

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Dumb question:
Why don't you just use the R43SG-TB3 which is exactly what you want, plus a FlexATX PSU or something like that? You can also use a Dell DA-2 brick and integrate it into your "Case"
 

Thehack

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I agree with using the R43SG. It should be able to handle all of your needs. It is also designed for 12V external so should work with RPS-200.

Sorry for the brain dump, but I've been researching this for a while and hit a few dead ends where my judgement has reached its limits. In particular the Cincon looks almost too good to be true compared to the RPS-200, but I'm afraid it'll fry my GPU and burn my house down because there's something in the spec sheet I missed. I'd appreciate a comment on that matter!

Is there anything wrong with just using a line switch at the AC plug to turn the PSU on and off? No PSU with less than 75 mm width seems to support PS_ON. Otherwise it should somehow be possible to control the DC side via the GxR-DIY or something similar. Does the GxR-DIY conditionally interrupt the 12V depending on say the PCIE header of the riser, or is it used to control the PS_ON signal on a PSU that has that functionality?

A slightly wider case, say 240 x 200 x 45 mm would probably solve all my issues because I could just go with a RPS-400-12 and call it a day, but I haven't found anything of the sort. Do they exist?

...and sorry for the double post; I can't seem to edit my previous post.

You can also use the CPS250, which is somewhere between RPS-200 and RPS-400 in design: https://www.artesyn.com/power-supplies/websheet/588/cps250-m-series. It does have PS_ON function.

The issue if you use something without PS_on via load switch (like GxR DIY) is that there is a small chance you still get stuck with the GPU always on problem. But this should be more of an ITX platform issue. If you're using NUC/mSTX it shouldn't be as much of an issue.
 

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R43SG is easier but not really necessary as long as you don't mind doing a little bit DIY.

You can do it cheaper (and smaller) with a normal M2 to PCIe adapter like OP had in mind and an PSU with H level PSon function like the RPS400.


Even without PSon function or GxR-DIY there is an cheap and easy workaround: just add an switch on the AC side of your PSU and turn the power for your eGPU on and off manually. Not exactly state of the art but does the job and you'll have zero standby power consumption. ;)
 

ermac318

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@ygrt

I think this would be the best solution for your build:


Just got one and tested it. Works like a charm together with the JEYI M2 to Thunderbolt adapter. No need load switch or PSon function. Just hook up some FLEX or 12V PSU and you are good to go.
How does it provide 3.3v with just a 12v PSU? Are you sure it works with only 12V? Most that have the SATA or Floppy connector do so because they need the 3.3V for pin 8
 

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How does it provide 3.3v with just a 12v PSU? Are you sure it works with only 12V? Most that have the SATA or Floppy connector do so because they need the 3.3V for pin 8

Yes, I'm sure it works. I have one of those sets for testing. You don't need 3.3V or 5V for your (e)GPU. They just use a SATA power adapter to grab 12V and feed the PCIe slot with that. The 3.3V rail is not used.
 

ygrt

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@ermac318 Fair question, the answer is obviously size ;) The R43SG is a fairly big board for what it does, and the Dell DA-2 brick is absolutely humongous compared to the RPS-200 or the CFM260. I'm aiming at 2 to 2.5 L total, including the PSU.

@REVOCCASES I might go with the dumb solution of just using a line switch on the AC side. Where do you see that the 3.3V pin is not connected on the Adt-link R43-ML?

@Thehack Actually I found a PSU that I like even more. Cincon enclosed PSU's use their case as heatsink. There's the medically rated CFM200M120C that hits 200W with 110V in a 2"x4" form factor with convection cooling alone. The only worry I have is that it has a ripple rating of 150mV, which is outside of ATX (120mV). Meanwell's EPP and RPS-200 are rated at 100mV ripple. I seem to remember seeing certification tests published by Meanwell indicating that in practise they're closer to 30mV, but I can't seem to find the test reports now. If the same trend held for the Cincon CFM series I'd be within a safe range, but I can't seem to find any test reports.

The CFM260S has less ripple (120mVp-p) than the CFM200M (150mVp-p), but I like the derating curve of the latter a bit better. Now I'm wondering what a ripple rating of 150mVp-p according to the data sheet means in practice, and if it would be an issue. I really want to move on with the project, but I'm a bit stuck. I requested the test reports from Cincon, but no answer so far.
 

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Where do you see that the 3.3V pin is not connected on the Adt-link R43-ML?

I have tested it. You only need 12V as you can see in my projects below. If you use the R43-ML (or similar) riser with a GPU, you do not need to connect 3.3V. The JEYI adapter I mentioned earlier even does not have those wires for 3.3V hooked up to the SATA power dongle. Some other PCIe devices might need that voltage but a graphics card does not.



 

ygrt

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Thanks, that makes sense. I was only aware of Jeyi's TB3 to M.2 cases. Is there a product site? The information from link you posted is a bit hard to parse.

Any thoughts on CFM260S vs CFM200M? I'm surprised the medically rated CFM200M has slightly higher ripple. Does 120 mV vs 150 mV ripple matter for a GPU? You'd hope that the real value would be a bit below that anyway.
 
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