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Thread: RX 5700 XT won't post in PCIE 4.0 / Auto mode

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    Senior Member cptwhite_uk's Avatar
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    RX 5700 XT won't post in PCIE 4.0 / Auto mode

    I bought the components of a PC that had suffered a PSU failure. Everything is booting as normal, except for the GPU. ...but I've had partial success with it.

    To cut a long story short I appear to have nailed down the issue somewhat. The GPU refuses to post when the PCIE interface is set to Auto mode (presumably PCI-E 4.0) when fitted into the top PCI-E x16 slot.

    I've tested with 3 motherboards, 3 power supplies, 3 sets of RAM, 2 display cables (DP and HDMI), different display outputs ports on the 5700XT.

    Firstly I tested in the motherboard it came with, MSI X570 gaming edge, it wouldn't post, so I switched out for a GTX 710, which booted fine. I tested in an old X79 Asus Rampage IV Extreme, no post. Tested in my main X570 system without removing Geforce drivers, no post screen still. Didn't expect it to work but I ran DDU to rid my main system of drivers, and to my surprise it booted into Windows and auto installed AMD drivers. I ran Kombustor for 5 minutes, all looked fine. I didn't check what PCI-E speed it was running it, but my board is set to Auto so I presume it would have been 4.0, but cannot verify. I was just happy the card ran without issues.

    I removed it, and tried in the X570 Gaming Edge and X79 again, neither would get a post. While on the X79 board I had the idea to limit it to PCI-E 2.0 (it's a 3.0 board), and it booted, set 3.0 manually and it wouldn't boot again. Partial result.

    However I intend to use it with the X570 gaming edge. I set it up with this mb again, no post, switched to PCI-E mode to 2.0, it posted, it also posted on the lower x16 slot on Auto. Then I set it to 3.0 in the top slot and got it to post, so that's the best result I've had so far.

    I could potentially just leave it at that if necessary, is only leaving ~5% performance on the table so it's not a deal breaker, but I'd still like to try and understand what's happening.

    I've updated the X570 BIOS, to no effect, so my next step is to update the GPU BIOS, and see if that changes behaviour. But after that my only options are to strip down the card and physically inspect for damage, or try cleaning the board and see if that has any effect.

    If anyone has any thoughts on this or ideas for me to try please let me know below.

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    HEXUS.social member Agent's Avatar
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    Re: RX 5700 XT won't post in PCIE 4.0 / Auto mode

    I'd be doing the same: GPU BIOS, then physical inspection.

    Random thoughts - You can see the X570 PCIe layout here: https://imgur.com/a/b7tntpZ#8Aug02l

    24 PCIe lanes on the CPU, minus 16 for the top GPU slot, which means you have 8 left. In other words, while the second slot is 16x in size, it's electrically 8x wired at best. There are some other considerations to know more (like what CPU, as they have their own limitations), but we don't really need to dig into it for this.

    I'm wondering if there is physical damage to the PCIe slot on the GPU, or the pull-up/down resistors just above it. These things:



    Physical damage to the pins on the card is normally easy so spot with a torch, but the resistors can sometime "cleanly" break off ,with a bit more attention needed to spot them. If any of these are missing, it could be that the card is 'kind of' communicating that it's 16x or a certain PCIe version, but the signalling doesn't match what it should, leading to a confused motherboard.
    Edit - just to complicate matters, by default PCIe will dynamically change the number of links to the GPU based on use to save power. Not much you can do with this information, but it makes troubleshooting a bit more muddy sometimes. You could try disabling the feature in the BIOS to see if that helps / makes it worse. Although I'm not sure what you could do with this, other than have it as another data point.

    Cleaning the pins with alcohol can also help.
    Last edited by Agent; 01-09-2023 at 07:55 PM.
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    Senior Member cptwhite_uk's Avatar
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    Re: RX 5700 XT won't post in PCIE 4.0 / Auto mode

    I think I've found the issue. I've successfully booted in the top slot, having used both Auto and forced PCI-E 4.0 settings in the BIOS. I'm not 100% sure of the reason, but I think I've isolated the point of failure. It might be a compatibility issue, having read online, or it might be damage from the power supply going kaput, but for now it's working as it should in the X570 board.

    I'll let you speculate a little more and will post my thoughts tomorrow

    Edit: Enthusiam was short lived. I was using a replacement 3200G, having used a 3700X when it would fail. I suspected PCI-E interface on the CPU was damaged, but it turns out the 3200G is only 3.0 compatible, so it was probably running in 3.0 mode, even though I was setting 4.0 in BIOS. Need to get hold of a 3000 series processor to see how it reacts with it, that will determine if it's the GPU or the CPU that's defective. It'll still run in 3.0 mode though, so it's not a massive issue even if it's the GPU.
    Last edited by cptwhite_uk; 01-09-2023 at 10:29 PM.

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    Senior Member cptwhite_uk's Avatar
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    Re: RX 5700 XT won't post in PCIE 4.0 / Auto mode

    Update:

    So I tested the exact same set of components - 3700X / Same RAM / X570 Gaming Edge / Top PCI-E slot / Known good PSU.

    MOBO and CPU are both PCI-E 4.0 x16 compliant. Since I didn't have a seperate 3000 series (not 3200G which is PCI-E 3.0), I kept the 3700X and tried with an RTX 3060 Ti which is PCI-E 4.0 compatible.

    The system boots fine with the 3060 Ti installed, so the issue is definitely with the 5700 XT and not the CPU.

    I've cleaned it up, re-pasted, cleaned the contact pins. I can't see any physical damage. It appears there's a couple of missing capacitors on the back of the GPU, but I've found reference photos online which suggest they're not populated on the reference card, and the're underneath the wishbone bracket in any case which would have shielded them from knocks, and the card had never been opened before (warranty stickers were still intact on the screws). So I believe this is a red herring.

    I've uploaded some photos of the physical card, and a comparison with the one you see in GamersNexus teardown of the exact same PCB. I can't see any differences / missing capacitors or damage.

    https://photos.app.goo.gl/DShcarizn5gUK68D7

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    Re: RX 5700 XT won't post in PCIE 4.0 / Auto mode

    RX5700's not one of these you can flash the BIOS on it it make it think/perform like another card?
    I'd stick it back in the board it booted with and check the BIOS on the card, maybe reflash it to whatever stock BIOS is meant to be on there.

  8. #6
    Senior Member cptwhite_uk's Avatar
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    Re: RX 5700 XT won't post in PCIE 4.0 / Auto mode

    It's happily running in PCI-E 3.0 mode. Once I've got the full system up and running I'll check the vBIOS and maybe try flashing it. It least I've found a work around and can replicate the problem now, thought I had a dead GPU at the start of this, so I'm happy regardless.

    Managed to get:

    X570 Gaming Edge
    RX 5700 XT Sapphire Nitro
    16Gb DDR4 3200 Corsair LPX
    Ryzen 3700X
    AMD Wraith Prism cooler

    ...all for £180 delivered
    Last edited by cptwhite_uk; 03-09-2023 at 09:52 AM.

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    Senior Member cptwhite_uk's Avatar
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    Re: RX 5700 XT won't post in PCIE 4.0 / Auto mode

    ...so just a quick update, I've set-up the full system now:

    I checked the vBIOS in GPU-Z and it suggests it's the same BIOS as the latest version available on techpowerup's database, so it didn't seem necessary to update it.

    The card will still only post in PCI-E 3.0 mode, and I've not traced the cause. It could be physical damage, but I can't see any. The issue can be replicated over different systems so the issue is definitely tied to the 5700XT itself.

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    Super Moderator Jonj1611's Avatar
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    Re: RX 5700 XT won't post in PCIE 4.0 / Auto mode

    Certainly looks that way. Though from looking at multiple benchmarks with Pci-e 3 vs 4 there is nothing in it so at least no performance loss
    Jon

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    Re: RX 5700 XT won't post in PCIE 4.0 / Auto mode

    For what it's worth, it looks like you're not the first person to have pcie 4 issues with this series:

    https://www.reddit.com/r/Amd/comment...uto_to_pcie_3/
    https://linustechtips.com/topic/1236...-5700xt-cards/
    https://community.amd.com/t5/graphic...ts/td-p/336290
    Quote Originally Posted by Saracen View Post
    And by trying to force me to like small pants, they've alienated me.

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