PCIe 4.0

As the first commerical x86 server CPU supporting PCIe 4.0, the I/O capabilities of second generation EPYC servers are top of the class. One PCIe 4.0 x16 offers up to 32 GB/s in both direction, so each socket offers up to 256 GB/s in both directions, for a full 128 PCIe 4.0 lanes per CPU. 

Each CPU has 8 x16 PCIe 4.0  links available which can be split up among up to 8 devices per PCIe root, as shown above. There is also full PCIe peer-to-peer support both within a single socket and across sockets.

With the previous generation, in order to enable a dual socket configuration, 64 PCIe lanes from each CPU were used to link them together. For EPYC, AMD still allows for 64 PCIe lanes to be used, but these are PCIe 4.0 lanes now. There is also another feature that AMD has here - socket-to-socket IF link bandwidth management - which allows OEM partners to design dual-socket systems with less socket-to-socket bandwidth and more PCIe lanes if needed. 

We also learned that there are in fact 129 PCIe 4.0 lanes on each CPU. On each CPU there is one extra PCIe lane for the BMC (the chip that controls the server). Considering we are living in the age of AI acceleration, the EPYC 7002 servers will be great as hosts for quite a few GPUs or TPUs. Density has never looked so fun.

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  • nathanddrews - Wednesday, August 7, 2019 - link

    Binned for OC? We'll find out soon enough!
  • DigitalFreak - Thursday, August 8, 2019 - link

    At this point it looks like all TR will get your is "official" ECC support and more PCIe lanes. Maybe cheaper motherboards than EPYC.
  • willis936 - Thursday, August 8, 2019 - link

    Half the memory lanes (this is a big one), half the pcie lanes, max of 1 socket per mobo. Those are important features for datacenter customers and their absence from threadripper makes threadripper less desirable than epyc in the datacenter.
  • rocky12345 - Thursday, August 8, 2019 - link

    Yes but Threadripper is made for high end desktops for video editing etc etc and some gaming. I do not see the big data center guys going after TR all that much. Yes you may see some of the TR go there but that is not what TR is made for that is why we have EPYC & XEON CPU's.

    I do have to agree though where some said where does TR fit in price wise since we are going to have a 16/32 main stream desktop CPU shortly from AMD. I do also think this time around the 32/64 3990 TR will be 10x better than the older 2990 TR just from the memory controller not being in each CPU complex and in the 2990x because of bandwidth and latency from the memory performance really suffered when all cores were being used. On the 3990x (or whatever it will be called) this should not be an issue. If AMD is smart they will not release a 64/128 3000 series TR since it would have to be priced to far out of reach for even the most techy guy with money and the only ones that would have them would be review sites and YT reviewers and that would be only because them got them sent for free for reviews. 32/64 and the better memory performance as a whole for the new chips would be more than enough to make the 32/64 TR 3990x an instant success. Just my opinion of coarse and AMD will probably do something stupid and release a higher core count TR series CPU that next to no one will be able to afford just to be able to say hey we got the best high end CPU on the planet but to bad no one is gonna buy them because the price is to high but we have the best so who cares.
  • rocky12345 - Thursday, August 8, 2019 - link

    Oops dammit forgot to make paragraph's did not mean to have it all bunched up like that.
  • Mark Rose - Friday, August 9, 2019 - link

    Why wouldn't they release a 64 core Threadripper? Assuming they double the price of the 32 core, it would be $3400. That's affordable to a lot of people working in tech, and should be affordable to just about any business that has employees waiting on their 32 core Threadripper. AMD would sell a ton.

    That being said, I wouldn't personally buy one as I don't have a need. I'd be more likely buy a 16 core 3000 series Threadripper myself.
  • Manch - Friday, August 9, 2019 - link

    Higher Clocks
  • sor - Wednesday, August 7, 2019 - link

    It will be a feature/packaging thing. The motherboards would be TR4 and feature enthusiast features, overclocked memory, etc, not highly reliable server oriented boards. The processors themselves might be fairly comparable to their EPYC counterparts, as some Xeons were occasionally comparable to their desktop ones.
  • close - Thursday, August 8, 2019 - link

    TR was supposed to be a stopgap measure until the consume Ryzen range stretched high enough and the server EPYC range stretched low enough. I guess there is a place for further differentiation especially in terms of the platform (motherboard) used, where you have server like CPU on a more consumer like MB to create basically a workstation. Maybe OC will also fit in here.
  • Death666Angel - Friday, August 9, 2019 - link

    "TR was supposed to be a stopgap measure" where can I see AMD stating that? Considering Intel has fared pretty well with the consumer/HEDT/server differentiation, I don't think AMD needs to axe TR. I don't see them giving us EPYC with OC functions and 8 memory channles seems overkill for 16 or 32 desktop cores. I also haven't seen a statement to the effect you claim, so I highly doubt it at the moment.

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