[sirlancer]

I was pleasantly surprised a few days ago to find Supermicro sells a 3U chassis that runs 8x Ryzen 7000 series CPUs supporting ECC. If one doesn’t need more than 128GB of RAM per system then they can get much higher clock speeds at a much lower power envelope than an EPYC CPU with an equivalent core count.

[JonChesterfield]

That should be a much higher power envelope, no? I'm struggling to think of a workload that would like eight 8/12/16 core systems on a network more than one 64 or 128 core chip on the grounds that latency is harder to find than bandwidth.

[adrian_b]

The performance per dollar of Ryzen 7950X is many times higher than of any Epyc or Threadripper CPUs, even after adding the costs of the motherboards, coolers, cases and PSUs.

The DRAM bandwidth per core is identical for Ryzen 7950X and for 96-core Genoa Epyc CPUs. On the other hand, the Epyc CPUs with high-core count have a better performance per watt.

So the initial cost for a cluster of Ryzen servers is many times less. Depending on the cost of electricity, if an Epyc server is used 24/7, after some years the expenses with it may become lower than with Ryzen.

If the server is used intermittently, the total cost of ownership may remain lower with Ryzen until the end of life.

The only certain advantages of Epyc are the ability of aggregating a higher amount of memory, especially if it is preferable to have it inside a single box, and the faster inter-core communication for applications that use all cores (as opposed to the case when the cores are partitioned between weakly-coupled applications, e.g. between different virtual machines).

The prices of the Epyc CPUs have increased a lot since their first generation until now.

With Zen 1, a server with any Ryzen would not have been competitive with a server with Epyc. Meanwhile, the ratio between the prices per core of Epyc and Ryzen has increased a lot, while the ratio between the performance per core of Epyc and Ryzen has decreased a lot, because the clock frequency of Ryzens has become much greater while that of Epycs has increased only a little.

These two evolutions combined have made that now the servers with Ryzen have become preferable to servers with Epyc in many cases.

AMD has realized that they no longer have a solution for cheap servers, so in theory they have introduced the Siena CPUs for this purpose. Nevertheless, those remain somewhat too expensive and moreover they are nowhere to be seen.