Andrew Cunningham
AMD’s AM4 socket has had a long and successful run on the desktop, ushering in the Ryzen processor family and helping AMD compete with and outperform Intel’s chips for the first time since the mid-2000s.
The days of the obsolete socket are coming to an end later this year when the Ryzen 7000 series chips are launched, but AMD is sending it off with one last powerful processor: the Ryzen 7 5800X3D, which launches on April 20 for $449.
AMD uses 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 feels like an experiment in some ways. Unlike other Ryzen CPUs, the 5800X3D offers no overclocking or power consumption control, and the clock speeds are a bit lower than the standard 5800X. But AMD says the extra cache allows the 5800X3D to beat Intel’s fastest CPUs when it comes to gaming.
We ran some tests on the 5800X3D to find its strengths and weaknesses and to get an idea of when you’ll notice the impact of the extra cache. This is undoubtedly a interesting processor, but its pricing and highly specific performance advantages will narrow it down to a niche of a niche.
3D V-Cache, in short
AMD
Architecturally, nothing has changed about the Zen 3 cores powering the 5800X3D compared to the vanilla 5800X. We’re still talking about an 8-core, 16-thread core complex that (CCD) built on TSMC’s 7nm process, with its 32MB L3 cache intact. Just as Apple built interconnection support into the M1 Max to support the M1 Ultra, AMD created Zen 3 to support 3D V-Cache technology when it was ready to ship.
The main change is that AMD and TSMC have lowered the physical height of the CCD die so that a CPU package with 3D V-Cache does not have to be physically larger than a CPU package without it. This change maintains compatibility with existing CPU coolers.
The 64MB additional L3 cache, also built on TSMC’s 7nm process, is physically stacked on the Zen 3 CCD and connected with direct copper-to-copper bonding. The result is something that the system sees as one large collection of L3 cache that can all be treated the same: the 64 MB stacked cache is not an L4 cache, and the 32 MB L3 cache built into the CCD has no performance advantage compared with the cache stacked on top of it.
AMD
A side effect of this packaging technology is that the 5800X3D has a noticeably lower clock speed than the 5800X, and AMD does not officially allow overclocking or power adjustments when using the 5800X3D. AMD is pushing the 5800X3D primarily as a gaming processor, and that’s because games more consistently take advantage of a larger cache pool to play with. For workloads that care less about cache and more about clock speed – as we’ll see when we start benchmarking – the 5800X3D can slower than the regular 5800X, which AMD freely admits.
| AMD’s 8-core Zen 3 CPUs | Street price | Clocks (Base/Boost) | L3 cache | TDP | PCIe support |
|---|---|---|---|---|---|
| Ryzen 7 5700G | $280-300 | 3.8/4.6 | 16MB | 65W | 3.0 |
| Ryzen 7 5700X | $299 | 3.4/4.6 | 32MB | 65W | 4.0 |
| Ryzen 7 5800X | $340-360 | 3.8/4.7 | 32MB | 105W | 4.0 |
| Ryzen 7 5800X3D | $449 | 3.4/4.5 | 96MB | 105W | 4.0 |
AMD played coy about whether we could expect future Zen 3 CPUs with 3D V-Cache enabled, but reading between the lines seems unlikely. 3D V-Cache will be one of the tools in AMD’s toolbox when it comes to improving performance for Zen 4 and the first Socket AM5 platforms – along with a 5nm TSMC process, DDR5 support and other architectural improvements – but I don’t get the feeling that the 5800X3D will be followed up with an expanded lineup of Zen 3 based X3D chips.
AMD says motherboards need a BIOS update to see and use the additional 64MB cache – look for AGESA version 1.2.0.6b or later in the release notes. Motherboards that support other Ryzen 5000 CPUs will work with the 5800X3D, but they can’t access the extra cache, negating the goal of spending more money on the CPU in the first place.
