In every motherboard generation on AMD's AM4 socket, we have seen a premium motherboard chipset and a more budget friendly chipset play out in the market. For the latest generation, focusing on Ryzen 3000 processors, we only have the X570 chipset in the market right now, and we're expecting to see a B550 chipset and motherboards built on that chipset at somepoint in the future. B550 hasn't been announced yet, but one avid Reddit user has spotted an OEM system built on the B550A chipset in stores. The existance of B550A has been verified by an AMD employee.

AMD’s B550A chipset belongs to the company’s Promontory-LP family (B450) and therefore supports 2+4 PCIe Gen 3 lanes, two USB 3.2 Gen 2 links, and six USB 2.0 connectors. The chipset is supposed to support overclocking, but since it is only available to OEMs, it is up to them to support the feature. The key capabilty of the B550A is that is has been validated to support AMD's Ryzen 3000 desktop processors.

One of the interesting things to note here is that AMD’s B550 chipset has not been announced yet. In fact, the existence of the B550A was confirmed by an AMD employee in a Reddit comment. It was confirmed that B550A is an OEM version of one of AMD's chipsets based on that Promontory-LP hardware. It is unknown at this point if B550 will act more like B550A, or rather like X570.

Image from Reddit

In the meantime, there a couple of words to say about OEMs and rebrands. One of the interesting things about big PC makers is that they demand product refreshes from their suppliers every year, which is why we see rebrandings of previously released products particularly in case of GPUs. To that end, the quiet introduction of AMD’s B550A chipset is not especially unusual, as it seems to only be OEM-bound. If nothing else, issuing a newer Promontory-class chipset for AMD's Ryzen 3000 CPUs gives OEMs another option for building reasonably-priced PCs powered by the latest processors.

Here is what AMD’s Robert Hallock had to say:

“It has a B550A motherboard. This is a version of the PCIe Gen 3 ‘Promontory-LP’ (e.g., X470, B450) chipset specifically for use in pre-built systems (e.g. OEM customers). […] OEMs are customers, too, and they may have different needs and wants than a DIYer. Not every product decision is considered through the lens of a channel product.”

Related Reading

Sources:, Toms Hardware, Reddit

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  • Colin1497 - Tuesday, October 15, 2019 - link

    "Meanwhile, the validation of a Promontory-class chipset for AMD's Ryzen 3000 CPUs enables OEMs to offer reasonably-priced PCs powered by the latest processors."

    This seems to be saying that the B450 isn't validated with the 3000 series CPUs?
  • brakdoo - Tuesday, October 15, 2019 - link

    AT needed to fill this page instead of just saying "B550a=B450/350 and B550(no a) is something else that we have to wait for".
  • Marlin1975 - Tuesday, October 15, 2019 - link

    I don't care if the chipset only supports PCIe 3.0. As long as the PCIe 4.0 from the CPU to the GPU, M.2 slot, and interconnect does that would be fine.
  • Death666Angel - Tuesday, October 15, 2019 - link

    The interconnect can't bet 4.0 (if you mean the CPU to chipset interconnect) since the chipset only supports 3.0 as stated. The other two things are up to mainboard developers and AMD allowing it (they blocked it for B450 and X470 etc.). I'd be fine with a B450 which has 3.0 lanes downstream, those 2.0 lanes really hurt it in my opinion. But I'm on X570 now anyway, so I don't really care anymore. :D
  • Hul8 - Tuesday, October 15, 2019 - link

    That's delusional.

    1) The B550A chipset would be used in OEM systems to cut costs (compared to a B550).

    Why would the OEM then go and spend those savings by routing the considerably more expensive PCIe 4 to the GPU and M.2?

    Also, take away market from a higher end model (with better margins) that could have a "real" B550 (if it ends up supporting PCIe 4 even partially) or an X570?

    2) The Promontory chipsets support PCIe 3 only upstream (from the CPU). All downstream PCIe is Gen 2. This means the jump in bandwidth would be up to 4x, for any 500 series PCIe 4 chipset.

    It's possible that B550 is what you want: It could have PCIe 4 support from the CPU, and between the CPU and chipset, but lower speeds from the chipset.
  • Marlin1975 - Tuesday, October 15, 2019 - link

    Thats what I meant, the consumer B550 not the OEM A one. If the B550 does not support at least some PCIe 4.0 then what does it really offer to most users over the sub $100 B450 boards now.

    Seems like the gap between the B450/X470 and X570 is large enough that the B550 will support some PCIe 4.0 but not full chipset support to fill that gap.
  • a5cent - Friday, October 18, 2019 - link

    "If the B550 does not support at least some PCIe 4.0 then what does it really offer to most users over the sub $100 B450 boards now."

    B450 is a PCIe 2.0 chipset. Not 3.0! Hopefully that's not all, but PCIe 3.0 instead of 2.0 is at least one of the things B550 would offer users over the sub $100 B450.

    The B450 is lacking in three areas:
    a) only PCIe 2.0
    b) the low number of PCIe lanes.
    c) an inability to directly drive a good number of modern USB ports.

    The lack of PCIe lanes is why B450 boards can't run two M.2 drives without downgrading the PCI x16 slot.

    If B550 maintains all the IO capabilities of X570 and merely lacks PCIe 4.0, then I'd say that's a very fair way of lowering cost without sacrificing features. That would be a great upgrade over B450, which looks very outdated to me. We'd be lucky if B550 is that good.
  • Valantar - Tuesday, October 15, 2019 - link

    What you're outlining there is pretty much the perfect scenario for retail B450 - a PCIe 4.0 x4 uplink to the CPU, and a decent amount of PCIe 3.0 lanes off the chipset - ideally enough for two x4 m.2 drives and a couple of controllers or slots. Though that would probably come too close to X570 for AMD's comfort, as you'd get >90% of its features for a significantly lower price.
  • Alexvrb - Tuesday, October 15, 2019 - link

    One of the M.2's can be directly connected to the CPU, so even if the uplink isn't 4.0 (and I think it should be) we get a 4.0 x4 M.2 plus 16 more 4.0 lanes which can be divided as board manufacturers please.
  • Hul8 - Monday, October 21, 2019 - link


    - in client space, PCIe4 doesn't have uses other than PCIe Gen4 x4 NVMe drives; and
    - the segment the B550 chipset targets would have little use for more than one such fast drive (if that)

    AMD and the motherboard manufacturers could optimize for cost/benefit by only using PCIe 4 for the primary M.2 slot, and having the GPU slot as well as chipset upstream and downstream connections be PCIe 3. Chipset could even have a mix of PCIe 3 and 2 downstream, for use in low bandwidth devices.

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