I don’t normally write “just” and “$ 4,000” in the same sentence. Most of the time, particularly in the CPU market, that kind of pricing is a contradiction in terms. At CES 2020, AMD announced that its upcoming 64-core CPU, the 3990X, will have a price tag of just $ 4,000.
To say that this undercuts Intel would be an understatement. The top-end Intel HEDT CPU you can purchase, the Core i9-10980XE, is $ 1,000 and packs 18 cores. A 2S Intel system built around the Xeon Platinum 8280 would offer 56 cores but has a sticker price of $ 20,000 just for the CPUs. AMD isn’t just undercutting Intel; they’re practically giving their top-end CPU away by comparison.
The 3990X has a 2.9GHz boost, a 4.3GHz max turbo, and an unknown all-core turbo (expected to be in the low-to-middling 3GHz territory). Scaling, at least in Cinebench, isn’t expected to be as good from the 32-core to 64-core mark, as shown below:
AMD’s claimed performance of ~25K is nearly 1.5x higher than the 3970X, but Cinebench has typically shown stronger scaling than this. Then again, we’ve never tested the application on this many cores, either. It’s possible that the poor scaling is just related to the application not addressing that many cores properly. There would be some historical precedent for this; Cinebench R10 scaled worse than R15, which was updated to provide better support for higher core count CPUs, among other things. It isn’t clear, in other words, if we should treat a 1.5x scaling gain as typical for the platform, and vendor benchmarks are always best taken with a grain of salt.
With just four RAM channels to feed 64 cores, the 3990X is more memory bandwidth constrained than the Ryzen 9 3950X is on AMD’s desktop platform, but the 3950X proved capable of running just fine with two memory channels.
Chips are set to ship on Feb. 7, which is earlier than I would have expected. AMD is recommending at least 64GB of RAM for these chips, but 128GB or 256GB might be more appropriate for relevant workloads, depending on how you intend to use it. The CPU will support DDR4-3200, but can technically be overclocked — though how the IMC will fare handling that much RAM is an open question. DDR4-3600 might be possible, though, and that would give the CPU an extra 1.13x memory bandwidth. If the CPU does suffer from bandwidth constraints, we should be able to test for it by checking performance against RAM clock relative to other CPUs in the Zen 2 family.
It’s not clear if there’s a Threadripper market for $ 4,000 CPUs outside of people who would just buy an Epyc to start with. But as a halo product, the 3990X offers a core count Intel can’t remotely match right now.
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