Review: Ryzen 7 5800X3D is an interesting tech demo that’s hard to recommend

The AMD AM4 socket has had a long history of success in desktop PCs, ushering in the Ryzen processor lineup and helping AMD compete and outperform Intel chips for the first time since the mid-2000s.

The time for legacy sockets is coming to an end later this year with the launch of the Ryzen 7000 series chips, but AMD is shipping them with the latest high-end processor: the Ryzen 7 5800X3D, which launches April 20 for $449.

AMD is using a unique packaging technology called “3D V-Cache”to triple the amount of L3 cache on the processor, from 32MB for the standard Ryzen 5800X to a whopping 96MB. This new technology seems to be an experiment in some way. Unlike other Ryzen processors, the 5800X3D offers no overclocking or power management options, and its clock speeds are slightly lower than the stock 5800X. But AMD says the extra cache keeps the 5800X3D ahead of Intel’s fastest processors when it comes to gaming.

We ran some tests on the 5800X3D to find its strengths and weaknesses and to understand when you’ll notice the effect of the extra cache. It’s certainly an interesting processor, but its pricing and highly specific performance advantages will limit it to a niche within a niche.

Briefly about 3D V-Cache

From an architectural point of view, the Zen 3 cores that run the 5800X3D are unchanged from the vanilla 5800X. We’re still talking about an 8-core, 16-thread-core (CCD) complex die built on TSMC’s 7nm process with 32MB of L3 cache. Just as Apple built connectivity into the M1 Max to support the M1 Ultra, AMD built Zen 3 to support 3D V-Cache technology when it’s ready to ship.

The main change is that AMD and TSMC have reduced the physical height of the CCD die so that a CPU case with 3D V-Cache does not have to be physically taller than a CPU case without it. This setting retains compatibility with existing CPU coolers.

64MB of additional L3 cache, also built on TSMC’s 7nm process, is physically placed on the Zen 3 CCD and connected by a direct copper-to-copper connection. As a result, the system sees one large pool of L3 cache that can be treated in the same way: 64 MB of L3 cache is not L4 cache, and 32 MB of L3 cache embedded in the CCD does not contain a performance advantage compared to the cache located on top.

One of the side effects of this layout technique is that the 5800X3D runs at a noticeably slower clock speed than the 5800X, and AMD doesn’t officially allow any sort of overclocking or power adjustment when using the 5800X3D. AMD is promoting the 5800X3D mainly as a gaming CPU, and that’s because games more consistently benefit from having a larger game cache pool. For workloads that care less about cache and more about clock speed – as we’ll see when we start testing – the 5800X3D can be slower than the regular 5800X, which AMD openly acknowledges.

AMD has been reticent about whether we can expect future Zen 3 processors with 3D V-Cache enabled, but reading between the lines it seems unlikely. 3D V-Cache will be one of the tools in AMD’s toolbox when it comes to performance improvements for the Zen 4 platforms and early Socket AM5 platforms – along with TSMC’s 5nm process, DDR5 support, and other architectural improvements – but I don’t get it. the feeling that the 5800X3D will be followed by an expanded line of X3D chips based on Zen 3.

AMD says motherboards will need a BIOS update to see and use the additional 64MB of cache – look for AGESA version 1.2.0.6b or higher in the release notes. Motherboards that support other Ryzen 5000 processors will work with the 5800X3D, but they won’t be able to access the extra cache, defeating the purpose of spending more money on a processor in the first place.