AMD EPYC 7251 Provides Great Value At Less Than $500 USD
Written by Michael Larabel in Processors on 17 October 2017. Page 1 of 6. 22 Comments

We have been delivering a number of EPYC 7601 Linux benchmarks since receiving this 32 core / 64 thread high-end server processor a little more than one month ago. Recently we received some additional EPYC processors from AMD for testing and for this next batch of benchmarking decided to begin with the EPYC 7251, which is the current lowest-end EPYC part. For priced at under $500 USD, this eight core / 16 thread processor has a lot to offer.

The EPYC 7251 is a 2P-capable part priced at $475 USD. This Zen server processor has eight cores / sixteen threads, 2.1GHz base frequency, 2.9GHz boost frequency, and 32MB of L3 cache. This is the lone EPYC processor to be limited to DDR4-2400 speeds rather than DDR4-2666 with the other EPYC CPUs, but still boasts eight memory channels. The TDP on this processor is 120 Watts, the lowest of all the EPYC CPUs. Like the other EPYC processors, the 7251 also supports 128 PCI Express 3.0 lanes.

On the Intel Xeon Scalable front at under $500 USD, the Xeon Silver 4112 is priced similarly at about $450~475 USD (though some retailers are selling it at up to $545 USD) but that is just a quad-core + HT, 2.6GHz base frequency, 3.0GHz turbo, 8.25MB L3 cache, six-channel DDR4-2400 support, and 85 Watt TDP. Or for eight cores to better go up against the EPYC 7251 in multi-threaded workloads is the Xeon Silver 4108 at $420~430+. The Silver 4108 is an eight core part plus Hyper Threading, 1.6GHz base frequency, 3.0GHz turbo frequency, 11MB L3 cache, 6 x DDR4-2444 support, and 85 Watt TDP.

For the price under $500 USD, the Xeon Silver 4108 is what I am using as the primary comparison to the EPYC 7251. Intel hadn't sent out any Xeon Silver review samples to Phoronix so I ended up purchasing the Xeon Silver 4108 for about $430 though at some retailers is closer to $470. So comparing the Xeon Silver 4108 and EPYC 7251, both are an eight core / sixteen thread design, the EPYC part has a higher base clock of 2.1GHz vs. 1.6GHz, the turbo/boost frequency of the Xeon Silver 4108 is slightly higher at 3.0GHz vs. 2.9GHz, the EPYC CPU has a much larger L3 cache size, the EPYC 7251 supports two additional memory channels, and the Silver 4108 has a lower TDP of 85 Watts versus 120 Watts.

Along with the Xeon Silver 4108, the processors tested in this latest Linux server CPU testing included the:

- Intel Xeon E3-1245 v5
- Intel Xeon E3-1280 v5
- Intel Xeon E5-1680 v3
- Intel Xeon E5-2609 v4
- Intel Xeon E5-2687W v3
- Intel Xeon Silver 4108
- AMD EPYC 7251

There are also tests on a few other EPYC CPU models coming up in future Phoronix articles in the days ahead as well as a complete look at all of the available Xeon / EPYC processors I have available for testing; this article was basically limited to the lower to mid-range parts.

The EPYC 7251 was tested with the TYAN Transport SX TN70A-B8026, which has been working out great in all of our EPYC tests to date. The TYAN 2U barebones server is paired with 8 x 16GB DDR4-2666 memory (albeit limited in this case to DDR4-2400) and for storage was using a Samsung 850 PRO SATA 3.0 SSD. All of these systems were running Ubuntu 17.10 paired with the Linux 4.13.6 kernel and GCC 7.2.0 as the main components worth noting off the Samsung 850 SSD with EXT4 file-system. All systems were forced to using the performance scaling governor. The CFLAGS/CXXFLAGS on each of the systems were set to "-O3 -march=native" with the Phoronix Test Suite automatically rebuilding the tests on each target.

As we've outlined in past articles, the AMD EPYC Linux support is basically in great shape. The only caveats to note is that not until the Linux 4.15 kernel is the AMD k10temp kernel driver extended to support CPU package temperatures (unfortunately, no per-core temperature reporting) for Zen-based processors if you are concerned about monitoring the CPU operating temperature. With Linux 4.14 is also where the initial bits landed for EPYC's Secure Memory Encryption.



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