B450 Pro4 PCIe conflict
Printed From: ASRock.com
Category: Technical Support
Forum Name: AMD Motherboards
Forum Description: Question about ASRock AMD motherboards
URL: https://forum.asrock.com/forum_posts.asp?TID=113455
Printed Date: 04 Apr 2026 at 12:41pm
Software Version: Web Wiz Forums 12.04 - http://www.webwizforums.com
Topic: B450 Pro4 PCIe conflict
Posted By: gordenf
Subject: B450 Pro4 PCIe conflict
Date Posted: 14 Feb 2026 at 7:47pm
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Hi, I have a problem with dual GPUs and nvme ssd in M2_2, it seems PCIE4 GPU conflicts with M2_2 nvme ssd. I had a pin-misdefined ssd(cant be recognized in M2_1), so I can only mount it into M2_2 with bios setting 'Force nvme for M2_2 Slot'. With one GPU mounted in PCIE2(3.0 x16), everything ran smoothly. Then I bought another GPU and mounted it into PCIE4(3.0 x4), found that Windows can't recognize the PCIE4 GPU. That was strange, as M2_2 has nothing related to PCIE4(which shares lanes with M2_1), as M2_2 shares lanes with sata3_3 and sata3_4. Then I tried turning off 'Force nvme for M2_2 Slot', not even removing ssd from M2_2, just rebooted(yes, this nvme ssd not showing in bios), booted another windows from ssd in sata3 slot, PCIE4 GPU showed in Taskmgr. Quite strange... so, any suggestion? CPU: R7 5700X MB: B450 Pro4, P10.43 beta(latest version) RAM: 32GB DDR4 3200 SSD: Kioxia EXCERIA PLUS G3 |
Replies:
Posted By: Xaltar
Date Posted: 16 Feb 2026 at 4:22pm
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I would guess that the setting to force NVMe for M2_2 disables the PCIe4 slot. NVMe uses 4 lanes where SATA3_3/4 only utilize a single lane between them. By forcing NVMe on M2_2 the other lanes need to be taken from the PCIe slot. You can https://tw.asrock.com/events/tsd.asp" rel="nofollow - open a support ticket and ask ASRock for a more definitive answer but based on your description that is what's happening. ------------- 
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Posted By: gordenf
Date Posted: 21 Feb 2026 at 2:27pm
| ahhh thanks! I checked the manual again, M2_2 uses 3.0x2，not 2.0x2 from chipset(as lanes of shared SATA was from chipset, so I only thought about chipset), and it all makes sense...M2_1, PCIE4, M2_2(NVME) share lanes. |
Posted By: garagedrive
Date Posted: 27 Feb 2026 at 2:34pm
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M2_2 uses only 2 lanes (3.0x2), so, SATA3_3 & 3_4 lanes sharing with M2_2 (3.0x2) make sense. 4th PCIe slot uses 4 lanes, so, PCIe 4th lanes sharing with M2_1 (3.0x4) make sense. I have the same problem (BIOS 10.43) when using PCIe 4-NVME conversion card. Can anyone solve this issue? I think it can be fixed by updating BIOS. |
Posted By: Xaltar
Date Posted: 27 Feb 2026 at 2:41pm
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That is something you would have to ask ASRock tech support directly: https://tw.asrock.com/events/tsd.asp" rel="nofollow - https://tw.asrock.com/events/tsd.asp -------------
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Posted By: garagedrive
Date Posted: 27 Feb 2026 at 3:05pm
| Now I see your point. M2_2 uses PCIe 3.0x2 from CPU, not PCIe 2.0x2 from B450 chipset. Lanes from CPU needs to be shared when utilizing M2_2. Thank you! |
Posted By: garagedrive
Date Posted: 02 Mar 2026 at 8:44pm
| By updating to beta BIOS 10.45 which Asrock Tech sent me, now I can use both M2_2 & PCIe 4th slot. Just FYI |
Posted By: Xaltar
Date Posted: 02 Mar 2026 at 9:27pm
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That is great news. ASRock's Tech Support is usually pretty good with this kind of request. Enjoy  -------------
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