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Thread: eGPU Power Supplies - cross loading and transient response time Q's

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    Default eGPU Power Supplies - cross loading and transient response time Q's

    So eGPUs seem to be an interesting use case for high quality power supplies and I am hoping that someone might have some info for me.

    So far, the best eGPU box I've found is the Razer Core v2 with the Enhance 1U 500W PSU but it is having issues with Radeon VEGA GPUs



    Issue:
    -Seems to cap out at around 350W on the 12V rail. Any higher and the box just shuts down during gaming
    -I can't figure out if the PSU can't handle the crossload or if it is the transient response time as the power draw will jump from 150 to 350w during gaming and typically just shut down. I have to unplug the eGPU, plug it back in, and i am back in business.

    If you load it on furmark (GPU stress test) it can sit fine at 375w+ so it seems to have issues with the quick jumps in power draw.

    Are there any ways to address this? Are there any PSU upgrades I could consider with very strong 12v rail? I saw awhile ago that ANTEC was using inline caps on the PCI-E cable which sounds like that might help... though obviously I'd prefer to figure out an easier solution.

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    I thought the issues Core v2 were having with Radeon VEGAs were heat related, not power.

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    Quote Originally Posted by jonnyGURU View Post
    I thought the issues Core v2 were having with Radeon VEGAs were heat related, not power.

    Definitely not heat - they do get toasty, though

    I've tested all three air cooled vegas

    Vega 56- works fine, even overclocked

    Vega 64- works fine at stock speed, overclocked the core will shut down randomly during gaming. I can overclock on furmark and pull down over 375w just fine but in games when the consumption jumps around from 150w to 350w+ the eGPU will shut down. This is really as far as the razer core will go.

    Vega Frontier Edition- This is the most power hungry card. It can't handle gaming at stock speeds without shutting down. Undervolting is a requirement to make it stable; any gaming will quickly shut down the egpu

    If anything, when things start getting hot, the VEGAs start power throttling so you actually draw less power when things start really getting toasty. If you take an overclocked vega and spin the fan all the way up to 4500rpm or something, it will crash much quicker because of increased power draw.

    Anywho - any suggestions on what to do? I thought about replacing the PSU fans but since it doesn't seem heat related, it doesn't make sense to do that.

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    Hmm... Could be just the way the PSU handles GPU transient loads from the VEGA. Would be worth while to try a different 1U PSU.

    You're sure that's a 1U, right.. and not custom? That ENH-2350 part number doesn't exist anywhere but in the Core.

    For my own curiosity, what do you have your Core plugged into? PC? Laptop? What motherboard/Thunderbolt interface?

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    Quote Originally Posted by jonnyGURU View Post
    Hmm... Could be just the way the PSU handles GPU transient loads from the VEGA. Would be worth while to try a different 1U PSU.

    You're sure that's a 1U, right.. and not custom? That ENH-2350 part number doesn't exist anywhere but in the Core.

    For my own curiosity, what do you have your Core plugged into? PC? Laptop? What motherboard/Thunderbolt interface?
    Hrm, ok, that thought does seem to mirror what I am seeing. I saw from an old review antec was putting capacitors in the PCI-E cable and you noted that actually made a difference. Is that something I could mod up and use to try and help with the load jumping around?

    Another eGPU brand, Mantiz, is taking FSP FSP550-50SGGBA power supplies and stating it is good for up to 375w power supply but not VEGA 64/FE.



    So I use the core on two devices, a macbook pro and a intel skullcanyon nuc.

    It's just a nice way I can have a portable device while still be able to game. Since I am using a macbook, an AMD GPU is a must.

    Lemme know if you have any other questions about thunderbolt 3 or eGPUs - it's very interesting what manufacturers are doing. The biggest unit is ASUS with a 600W 1U while HP repurposes an OEM lite-on unit.

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    I think it was Igor over at Tom's Hardware that really showed that those caps in the cables made a bit of difference. I can certainly see how that's the case.

    We see this in other examples as well. Apparently using multiple Nvidia Teslas in a workstation has a similar effect. Some PSUs work, others don't. Wonder if the caps would address that issue as well.

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    Quote Originally Posted by jonnyGURU View Post
    I think it was Igor over at Tom's Hardware that really showed that those caps in the cables made a bit of difference. I can certainly see how that's the case.

    We see this in other examples as well. Apparently using multiple Nvidia Teslas in a workstation has a similar effect. Some PSUs work, others don't. Wonder if the caps would address that issue as well.
    Know of any places that sells custom cables that allows capacitor add-ons?

    I'd give that a shot, seems easy enough...

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    Just buy the caps and splice them in. I've done it before.

    Just make sure to get the polarity of the cap right. I've also done that (incorrectly) before.

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    Quote Originally Posted by jonnyGURU View Post
    Just buy the caps and splice them in. I've done it before.

    Just make sure to get the polarity of the cap right. I've also done that (incorrectly) before.
    Now we are talking!

    Any good guides on how to do this so I don't screw this up?

    Three caps? One for each 12V? Any suggestion on cap size/brand? I have room, so I can go big...

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    Antec uses a single 2200uF 16V cap. I think it was just tapped into one +12V and one ground. You could probably Google some photos.

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