AM5 platform gets official support for server use
Some time ago we reported that AMD is preparing a low-cost server processor platform based on the AM5 desktop socket, derived from Ryzen CPUs. This has now been confirmed, the company has officially launched these processors as Epyc 4004. They can have up to 16 cores as well as V-Cache, but there is even a quad-core model, which you won’t normally find in a desktop. Otherwise, though, these the specs closely match Ryzen SKUs for PC.
The Epyc 4000 is intended to be an affordable (cost-optimized) server platform for small and medium-sized businesses. This is achieved by utilising similar hardware to that used in desktop PCs and the AM5 socket, but with added server features – i.e. RAS features, official ECC memory support, but also various security features from Ryzen Pro.
AMD desktop processors use CPU chiplets that are also used in the big server processors, which simplifies this. Consumer IO dies used in Ryzen processors, while a separate design, probably differ mainly in the amount of connectivity blocks and memory controllers, while the IP used probably share a lot of DNA with the server IO dies.
The Epyc 4004 is the first generation to be offered as this low-cost desktop-derived basic server platform. However, the 4 at the end signals that it uses the Zen 4 architecture (like Ryzen 7000X), the eventual next generation with Zen 5 cores would be called the Epyc 4005.
This means that the basic specifications are very similar to Ryzen 7000(X) processors. The processor has up to 16 cores (32 threads) of the Zen 4 architecture. The memory controller supports DDR5-5200 (officially with ECC) and is dual-channel (128 bits wide), if we use the traditional designation. Officially, the supported RAM capacity is 192GB with four 48GB modules, but it is possible that eventually 64GB ECC modules will be validated too, giving a max total of 256GB of RAM.
The connectivity of the socket is up to 28 PCI Express 5.0 lanes, but four of those lanes will usually be taken by an additional chipset (B650E, X670E for example). The processors should retain the integrated graphics from Ryzen 7000, which is a small GPU with RDNA 2 architecture with 128 shaders. This allows a monitor to be connected via HDMI 2.1 or DisplayPort 2.1 (UHBR10), so these processors can be used for certain workstation tasks where a powerful GPU is not needed.
Models: V-Cache, a quad-core too
The individual Epyc 4004 models seem to be pretty much replicating the Ryzen SKU configurations. The top of the range is the Epyc 4564P with 16 cores/32 threads and 170W TDP. Its clock speeds are 4.5 GHz base and 5.7 GHz maximum (usually single-threaded) boost, which exactly matches the Ryzen 9 7950X. It even has the same official price as the Ryzen 9 7950X (before price-cuts happened): 699 USD.
But the second most powerful, 12-core model is a 65W one and is based on the Ryzen 9 7900 instead of the 170W 7900X. Again, the clock speeds are an exact match: 3.7–5.4 GHz. It goes on like this with the other SKUs, there are the server equivalents of the 105W Ryzen 7 7700X and the 65W Ryzen 7 7700 with eight cores and the 65W Ryzen 7600 with six cores, again the clock speeds match in each case.
But there is one specialty, which is a quad-core model, designated Epyc 4124P, at the very bottom of the range. It has four cores, eight threads, but only 16 MB of L3 cache instead of the usual 32 MB. In this SKU, AMD apparently uses those chiplets that had a manufacturing defect on the wafer somewhere in the L3 cache region, but shutting down some of the blocks allows them to be used. The TDP is 65 W and the clock speeds are like those of the Ryzen 5 7600 (or the Epyc 4244P hexa-core derived from it), 3.8 GHz base and 5.1 GHz boost.
As far as we know, there is no equivalent quad-core in the Ryzen 7000 series (it would probably be the Ryzen 7300 if it existed, or the 7300X that was once rumored, but it turned out to be fake). The price of this quad-core is 149 USD.
X models have 3D V-Cache on only one of the chiplets
Two models with V-Cache are also included in the range. When the news of the imminent arrival of these processors appeared, we did not know that, except for that quad-core, there would be no differences in configurations compared to the desktop models and there were hopes that there could be processors with 16 cores and V-Cache on both CPU chiplets (i.e. 2 × 96 MB). Unfortunately, this did not materialize.
The two models with 3D V-Cache – the Epyc 4584PX with 16 cores and the 4484PX with 12 cores fully match the Ryzen 9 7950X3D and the Ryzen 9 7900X3D, including clock speeds (4.2–5.7 GHz and 4.4–5.6 GHz). They also have a claimed total L3 cache capacity of just 128 MB, which means that V-Cache is only on one of the CPU chiplets and thus only half of the cores directly benefit from it (this also means that the other half of the CPU cores, in turn, is capable of boosting higher, while the cores with V-Cache will max out at just above 5.0 GHz).
AMD doesn’t offer – at least not yet – an Epyc server version of the Ryzen 7 7800X3D that wouldn’t suffer from this – it would have just eight cores, but they would have uniform performance characteristics, i.e. all would have access to 96MB of unified L3 cache and similar clocks. According to ServeTheHome, the Ryzen 7 7800X3D is actually quite attractive for cheap server builds, so an improptu solution may be to simply use this mainstream gaming CPU, however, as mentioned above, that would lack full server validation and officially guaranteed ECC support (although it will probably still work in a server board without any problems).
Compatibility with Ryzen 7000
These processors don’t require outright new boards, and could probably be compatible with regular consumer boards after a BIOS update (but then you’d probably miss the infrastructure of RAS functions). Ryzen CPUs on the AM4 and AM5 platform were actually already used as popular cheap server solution and there do exist server boards for them. So the Epyc 4004 CPUs will pretty much just come to these existing platforms, though some new boards and servers will probably appear as well. For example, Gigabyte or ASRock Rack have already announced BIOS updates that will make Epyc processors work with those of their existing AM5 boards that target server usage.
In any case, these processors have now been rolled out and should be available now. According to AMD, servers and motherboards such as Supermicro, Tyan, ASRock Rack, Gigabyte, MSI, Lenovo will support them or already do.
A problem for Intel?
This line-up catches Intel a little bit off guard, because its alternative (Xeon E) that is also based on desktop processors uses “big.LITTLE” hybrid architecture. These processors only have eight high-performance P-Cores versus the 16 cores of Ryzen (and now Epyc 4004). While the hybrid concept seems to work relatively well in desktop, that’s not as true in servers, and the Xeon E-2400s that are Intel’s solution competing against these new Epyc 4004s always only have at best eight P-Cores enabled.
According to for example, Patrick Kennedy of ServeTheHome, the Epyc 4004 will severely outclass Intel in this segment. (But note that this doesn’t mean Intel it can’t retain perhaps as much 75% of the market, purely due to market inertia, branding and long-term positioning and so on, so fart he market has been working like that).
English translation and edit by Jozef Dudáš
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