X570 Phantom Gaming-ITX/TB3 Bifurcation
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=22376
Printed Date: 03 Aug 2025 at 4:55pm
Software Version: Web Wiz Forums 12.04 - http://www.webwizforums.com
Topic: X570 Phantom Gaming-ITX/TB3 Bifurcation
Posted By: Ninja1283
Subject: X570 Phantom Gaming-ITX/TB3 Bifurcation
Date Posted: 25 Mar 2022 at 6:08pm
Can someone answer a few questions about bifurcation options on this motherboard, or direct me to where I can get these answers? I have tried reaching out directly to the ASRock technical support team, but my point of contact has been unhelpful, unprofessional, and has provided false/conflicting information thus far.
Specs:
MB: http://www.asrock.com/MB/AMD/X570%20Phantom%20Gaming-ITXTB3/" rel="nofollow - X570 Phantom Gaming-ITX/TB3
Processor: https://www.amd.com/en/products/apu/amd-ryzen-5-pro-4650g" rel="nofollow - Ryzen 5 Pro 4650G
BIOS: http://www.asrock.com/MB/AMD/X570%20Phantom%20Gaming-ITXTB3/#BIOS" rel="nofollow - P3.50 (latest version as of post)
I have a U.2 drive connected to the rear M.2 slot, and a https://www.amazon.com/gp/product/B09N92SQY9/" rel="nofollow - PCIe x16 to (4) M.2 adapter installed in the PCIe slot. This adapter is populated with four M.2 drives, all verified to be functional in another system, as well as individually in this system, using the carrier board. I am trying to enable bifurcation to see all four drives in the carrier board, but can only see 2-3, depending on what bifurcation options I select in the BIOS.
- Under the PBS settings, the "PCIe x16 Switch" option has changed to " https://imgur.com/ZtgF9QD" rel="nofollow - PCIe x8 Switch ". I know the older (1-2 gen) APUs only had 8 lanes dedicated to the PCIe slot, but the third gen and beyond (4xxxG, 5xxxG, etc) should have 16 lanes. Is this just a typo/BIOS mistake by ASRock, an AGESA issue, or something I missed? https://imgur.com/CAEGEJ9" rel="nofollow - All of the headers seem to indicate only PCIe x8, but all of the menu options would indicate full x16.
- If I turn of bifurcation completely, I can see one drive. If I select "2x8", I can see two drives. If I select "2x4 1x8" or "1x8 2x4", I can see three drives. However, if I select 4x4, I am only able to see two drives. Is 4x4 (4x/4x/4x/4x) bifurcation actually implemented on this motherboard? If so, do I need a newer/different CPU or BIOS? I have the latest BIOS, and the 4000 series G processor I'm using should have 16 lanes connected to the PCIe slot, so I don't think either of those would be a limiting factor, unless I'm missing something.
So my questions are:
- Is there any reason why this MB + APU combination shouldn't be able to bifurcate @ 4x4 correctly?
- If so, any ideas on what I need to change?
- If not, what CPU/BIOS/etc combination do I need in order to gain full 4x4 bifurcation as indicated in the BIOS option?
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Replies:
Posted By: threadzipper1957
Date Posted: 08 Aug 2022 at 8:03pm
As far as I know, the first PCIE slot (in this case the only slot) is connected to the CPU together with the first M.2, but that is based on a block diagram of another X570 board.
The available modes 1x 8 or 2x 4 lanes, is under AMD PBS, and what you need to understand is that AMD CBS and AMD PBS are integrated in the Agesa code that AMD creates, so a manufacturer doesn't have the option to change this.
The PCIE slot provides 16 lanes, and can only be divided into 2x 8, but what you need is 4x4, and that is simply not possible, it is also written in the specs of the board
***Supports PCIe riser cards to extend one x16 slot to two x8 slots if you install AMD Ryzen series CPUs***
The CPU, provides a number of PCIE lanes, but some of them also have to be assigned to certain resources, for instance a Thunderbolt controller.
You cannot simnply say, that when the CPU provides more lanes, this would enable bifurcation.
For bifurcation, you need also enable the NVME RAID mode, this in combination, with the bifurcation, allows you to see the M.2 as individual drives.
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Kind Regards
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