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AMD EPYC 7251 Provides Great Value At Less Than $500 USD

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  • #11
    Typos:

    Originally posted by phoronix View Post
    6 x DDR4-244 support
    Originally posted by phoronix View Post
    and the continuining limited availability of EPYC processors from Internet retailers thus far.

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    • #12
      Would it be possible to setup Ryzen CPUs (Threadripper probably) with multiple GPUs and virtualize gaming desktops there for an entire family? I would put the machine in a rack, provide each family member with 16GB RAM + 4 cores and dedicated GPU. Is it a viable solution? How the video from the VM would be streamed to cut on the latency?

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      • #13
        Originally posted by schmidtbag View Post
        But Epyc was often outperforming (or close to it) the Xeons of similar core counts and/or frequencies. So even ignoring price point, Epyc was still doing oddly very good, and I'm not sure the extra memory channels are enough. But maybe I'm wrong - this is why I'm interested in an IPC test against Ryzen.
        Comparing these 7251 tests with the 1950X threadripper and 1800X benchmarks of Rodinia OpenMP LavaMD, the 1800X/1950X tests have [email protected] and this test has [email protected], which is a significant difference in memory speed. It seems like despite having a base frequency that's ~40% lower than the 1800X, but having twice the amount of L3 cache, the 7251 is ~20% slower than the 1800X. If the 7251 was clocked higher, I'd imagine it would beat the 1800X handily and by 20+% (clock for clock, and given the dissimilar RAM speeds). That difference would be in line with having twice the amount of cache, and 4x the amount of memory controllers/bandwidth. But Rodinia doesn't seem like it's memory intensive, so this difference is likely just because of doubling the cache. IPC wise, it seems pretty in line. Doubling the cache would make around that much of a difference or greater. I'm not sure how much RAM/infinity fabric speed would matter in this CPU intensive benchmark either, IMHO.

        I'm not sure what the comparision with the 1950X shows, apart from having 2x cores and 32MB L3, gives you almost 2x the performance in the CPU bound test.

        1800X/1950X Rodinia benchmark: https://www.phoronix.com/scan.php?pa...tr-1950x&num=3
        7251 Rodinia benchmark: https://www.phoronix.com/scan.php?pa...pyc-7251&num=2
        Last edited by audir8; 17 October 2017, 03:27 PM.

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        • #14
          Originally posted by killyou View Post
          Would it be possible to setup Ryzen CPUs (Threadripper probably) with multiple GPUs and virtualize gaming desktops there for an entire family? I would put the machine in a rack, provide each family member with 16GB RAM + 4 cores and dedicated GPU. Is it a viable solution?
          Yes, this is doable and if done properly it would work pretty well. Multi-seat setups have been around for a while and there are dozens of guides for them, but they're a real PITA to set up. If this is supposed to act as a family PC though, I think 16GB per person is seriously overkill. Even 8GB would be plenty, unless you intend to do a lot of modern gaming. If you don't use a VM (it is possible to do multi-seat in Linux without VMs), you could definitely get by with 8GB per user, since you'll have a lot of shared memory.
          How the video from the VM would be streamed to cut on the latency?
          The best route is to do GPU-passthrough (meaning IOMMU needs to be enabled from the BIOS), where you're detaching the GPU from the host OS and making it only visible/usable to the guest. That implies you will either need a GPU for the host, or, the host will need to be accessed via SSH in order to maintain it while guests are still running. I don't think most multiseat setups run a seat on the host. Anyway, since each user gets their own direct access to a GPU, latency is hardly a problem. But if you care about things like VR or playing games like CS:GO, I'd advise against multi-seat.

          I know Xen has proven to work in the way you're imagining. Might want to look into that.
          Last edited by schmidtbag; 17 October 2017, 03:33 PM.

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          • #15
            Wow. EPYC is such a robust platform. 8 channel memory, 128 PCI-E 3 memory lanes, and really excellent processing power to boot. If I had the 32 core variant I'd be set for 10 years.

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            • #16
              "The EPYC 7251 is a 2P-capable part priced ...."

              Is it supposed to be obvious what '2p-capable' means .. ????

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              • #17
                Originally posted by orzel View Post
                "The EPYC 7251 is a 2P-capable part priced ...."

                Is it supposed to be obvious what '2p-capable' means .. ????
                Can be used with Epyc dual socket motherboards if wanting to run two of them; not all EPYC parts are able to be used in a dual socket configuration (the 1P parts).
                Michael Larabel
                https://www.michaellarabel.com/

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                • #18
                  Meh.Using Epyc for CPU muscle alone doesn't make much sense. It's low frequency part that doesn't have that much to offer if anyone doesn't need extra PCIe lanes, ECC, 2-socket suport and quad-channel RAM. And those extra RAM channels count for something only if one needs ECC and register, otherwise they might not be such a bandwidth upgrade over two smokin fast DDR4 channels.

                  These things are for apps that absolutely must have an access to big amounts of RAM and need two sockets to do that, possibly through several boards, interconnected with Infiniband or similar glue.

                  For one onbard/one socket solution, Threadripper would smoke it. 1950x is twice the price of 7251, but that will diminish once you factor in price of board + RAM.
                  And at that ptice, 1950x offers almost four times of CPU muscle -ie 2x cores at almost 2x speed...


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                  • #19
                    I beg to differ with the "Great Value" claim; both Xeons mentioned, the Silver 4108 and the Silver 4112 have AVX-512 support, Epyc cpu's do not, in many floating point heavy applications, such as those in HPC workloads like various simulation type workloads, the Xeons will simply walk away from Epyc's.

                    So long as AMD continues to make processors based on a competitors ISA technology, they will continue to be in second place in market share, revenue and performance.

                    Perhaps AMD should have focused on their ARM based Opteron line, grow that market, as it seems that ARM is the future, hell it's even rumored that Apple is developing their own ARM based cpu to replace Intel's processors in the Apple desktops.

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                    • #20
                      Originally posted by schmidtbag View Post
                      I don't know if it's just because the frequencies are different, but I find it odd how Epyc seems to be so much better than Xeon, whereas Ryzen is underwhelming compared to the Core i series.

                      Michael: Might be interesting to see an IPC test of Ryzen vs Epyc, with the 8700K and the Xeon Silver included in the mix too.
                      Two possibilities:
                      1. With the Xeon line, Intel doesn't have the huge clockspeed lead over AMD. Most of the reason why 7700k or 8700k seem to be "so great" is because they are clocked right near their silicon limit, 15-20% over their Ryzen competition.
                      2. SkyLake-X vs SkyLake. AVX-512 notwithstanding, having bigger slower L2 cache and mighty slower, smaller L3 cache might actually cause performance regressions in certain workloads.

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