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PCIe 4.0 May Come to all AMD Socket AM4 Motherboards (Updated)

Update: We spoke with AMD representatives, who confirmed that 300- and 400-series AM4 motherboards can support PCIe 4.0. AMD will not lock the out feature, instead it will be up to motherboard vendors to validate and qualify the faster standard on its motherboards on a case-by-case basis. Motherboard vendors that do support the feature will enable it through BIOS updates, but those updates will come at the discretion of the vendor. As mentioned below, support could be limited to slots based upon board, switch, and mux layouts.

Original Article:

AMD set enthusiasts' hearts alight today when it announced its 7nm Ryzen 3000-series processors. These new processors come bearing the 7nm process, the world's smallest for desktop PCs, which will lead to reduced power consumption and heat, but they also support PCIe 4.0, giving AMD yet another advantage over Intel's lineup.

At its CES keynote, AMD reiterated its guarantee of support for the Socket AM4 motherboards until 2020, so the new Ryzen processors will be backward compatible with the existing motherboards, but with a caveat: AMD says you will lose support for PCIe 4.0 on its older platforms.

But after speaking with several motherboard vendors here at CES 2019, we've learned that many of them have successfully tested PCIe 4.0 on 300- and 400-series AMD motherboards, meaning that the feature could be enabled with a simple BIOS update, at least partially.

Our sources tell us that after unlocking the feature via a BIOS update, the older motherboards supply a PCIe 4.0 x16 connection to the first slot on the motherboard, but the remainder of the slots revert to PCIe 3.0 signaling rates. That's because any trace routing on the motherboard that exceeds six inches requires newer redrivers and retimers that support PCIe 4.0's faster signaling rates. That means the PCIe slot nearest to the CPU will easily support PCIe 4.0, while the other slots, including M.2 ports, will run at a PCIe 3.0 signaling rate.

The 500-Series chipsets will consume more power (~15W) than the 28nm chipsets (~8W) used on current AM4 motherboards, but that's because the 500-series chipsets also support PCIe 4.0. We weren't told the specific lane allocations of the new chipset, but those faster lanes will be useful for numerous types of secondary I/O devices.

We're also told by motherboard vendors that AMD will stop using ASMedia to design its chipsets. But AMD says that it will continue to use ASMedia, but the new chipsets will be "more nuanced." That could mean that AMD will design parts of the chipset and simply license key IP blocks, like USB 3.1, from ASMedia.

Even though multiple board partners have tested PCIe 4.0 on previous-gen chipsets, it remains to be seen if AMD will allow them to expose that functionality via BIOS updates. Our sources tell us that AMD can simply lock out that feature and that the fate of PCIe 4.0 support on 300- and 400-series motherboards haven't been communicated to them yet.

We'll update as we learn more.

  • mikewinddale
    I'd like to know how many PCIe 3.0 lanes Ryzen 3xxx will have. It's kind of depressing when your motherboard tells you that the second M.2 is only PCIe 2.0, and that installing a second M.2 disables one of the PCIe slots. I'd like to have enough PCIe 3.0 lanes to fill up all my M.2 and PCIe slots. Or at least enough that filling one slot doesn't entirely disable another.
    Reply
  • ricardoarredondoa
    6th Paragraph down "Our sources tell us that AMD can simply lock out that feature and that the fate of PCIe 4.0 support on 200- and 300-series motherboards haven't been communicated to them yet" Should be "300- and 400-" instead of "200- and 300-"
    Reply
  • shrapnel_indie
    It will be interesting to see what comes of it with the older boards... Most of us probably won't be able to benefit from it in the immediate future anyway.
    Reply
  • LinuxDevice
    Right now even the fastest video card isn't bottlenecked on PCIe v3. I suspect it will be a long time before anything "consumer" uses PCIe v4. However, there's a new generation of 100Gb/s networking that might suddenly have meaning (and perhaps controllers of massive storage warehouses).

    Someone else asked a question about how many lanes though...I imagine that if suddenly a video card works with PCIe v4 and runs at full speed even with x4 or x8 it'll free up lanes for other uses.
    Reply
  • jimmysmitty
    21661189 said:
    I'd like to know how many PCIe 3.0 lanes Ryzen 3xxx will have. It's kind of depressing when your motherboard tells you that the second M.2 is only PCIe 2.0, and that installing a second M.2 disables one of the PCIe slots. I'd like to have enough PCIe 3.0 lanes to fill up all my M.2 and PCIe slots. Or at least enough that filling one slot doesn't entirely disable another.

    I will assume same as before, 16 lanes and 4 for M.2 NVMe drives with any others being fed by the chipset, possibly the chipset will be upgraded to PCIe 3.0 or I hope as thats one advantage Intel has had.

    21661449 said:
    It will be interesting to see what comes of it with the older boards... Most of us probably won't be able to benefit from it in the immediate future anyway.

    By the time we would benefit from PCIe 4.0 AM4 will be a dead socket.
    Reply
  • none12345
    Not needed, but cool if true. Ill take a free upgrade to pci4! No need to buy a new mobo if true, tho ill probably still buy one to replace another old system.

    Looking at that 8 core vs 9900k demo...cant wait for a 12 core zen2 chip. I dont really need it, i just want it. At least i want a 12 core ~4.7+ ghz chip.
    Reply
  • hannibal
    Does the amd need 12 to 16 cores now? They can definitely do it, but is there any economical reason for that at this moment? Maybe normal 8 core versions 2019 and two cpu 16 core version at 2020, when 7nm is cheaper to produce? They already have Intel in trouble at this moment.
    Also how hard it would be make old chipsets compatible with 16 core Ryzen 3000? I am sure that x570 could make it, but can older 300 and 400 series? There Are Many interesting thing to find out.
    We can be sure that we see 16 cores at least in am5 processor socket or what ever comes after am4. But Until that there Are some backward compatibility issues that has to be maintained. Maybe it is possible maybe not. We don`t know yet.
    Reply
  • bigpinkdragon286
    Thanks for the well tempered article. Finally, a good mix of crystal ball and good sense that doesn't conflict so much with reality, while actually bringing a welcome message.

    Maybe it's wishful thinking, but I was certainly hoping that at least some limited PCIe 4 functionality would make it's way to at least some of the currently existing crop of AM4 motherboards. While there's no guarantee, it's encouraging that I'm not the only one having similar thoughts in this regard.

    Folks tend to forget that, while nothing may need the extra ability provided by PCIe Gen 4, having more resources available for a PC's disposal isn't going to hurt anything, and usually results in a smoother, cooler, less bogged machine under heavily loaded situations, or in the case of peripheral buses, allows other devices access to resources more often, as the bus can be freed up sooner for use by other devices.

    It may seem wasteful to be unable to fully utilize the newer bus speeds, but as we've seen in the past, such as when the first UDMA hard drives hit the market, there were quality of life style improvements as the overhead for using the hard disk started to diminish, resulting in what can only be described as a smoother operation of the overall system.
    Reply
  • Olle P
    Nice for us early adopters if true, but it will take a while Before i get any attached device that can make use of PCIe 4 anyway. (Just like I have very few USB3 devices but many USB2.)

    21663303 said:
    Does the amd need 12 to 16 cores now? They can definitely do it, but is there any economical reason for that at this moment?
    If you by "this moment" mean "more than half a year from now" and there then will be a market for it: Yes!

    Reply
  • InvalidError
    21661189 said:
    I'd like to know how many PCIe 3.0 lanes Ryzen 3xxx will have.
    Changing the number of CPU-hosted PCIe lanes would most likely require a new socket and definitely require a new motherboard to re-route whatever pins get re-purposed for those if it was done on AM4, so don't expect the number of PCIe lanes to change until AM5 or whatever AMD's next socket ends up being called.
    Reply