Intel’s 28-Core Overclockable Xeon Finally Available, Put Through Its Paces

Intel’s early efforts at marketing its 28-core desktop Xeon processor didn’t get off to a great start. The company was dragged for demonstrating a 5GHz CPU at Computex without immediately disclosing that the CPU in question was being cooled with a 1.7kW water chiller. The final product to come out of that initial mess is the Xeon W-3175X. The good news is, it’s a much better part than its initial debut suggested — if you have the wallet for it, and the power budget.

First off, let’s talk about the price. First, we heard rumors of high single-digit pricing, before a $4,500 target leaked. The actual price Intel is launching the W-3175X at is $2,999. At that price, it’s actually a slightly better deal (in terms of price-per-core) than the 18-core Core i9-9980XE, at $111 for the 18-core chip and $107 per-core for the W-3175X. The W-3175X also has a higher turbo mode clock than the 18-core Core i9-9980XE, topping out at 4GHz when loaded with 18 threads, compared to the 9980XE, which holds 3.4GHz in that same configuration.

As Anandtech discusses, that price is key to the overall value proposition presented by the Xeon W-3175X. The CPU’s power consumption is very high — the 255W TDP only applies to the stock clock. At load using Intel defaults, the CPU pulls roughly 315W. If you allow the motherboard to use more aggressive settings (see this discussion on TDP for more details), the chip will pull as much as 380W. Start overclocking, and you’ll crack 500W without much trouble. In all cases, these figures refer only to the CPU, not overall system power consumption. According to Ian Cutress at Anandtech, you’d need the massive cooler Intel used at Computex if you actually wanted to push the CPU up to a theoretical 5GHz.

These are chips that will only be sold to OEMs for inclusion in full desktops; Intel isn’t planning to bring these chips to the retail market at all. Anandtech’s overall evaluation, however, is positive, and the relatively low price is key to that point.

At $4,500 or above, the chip is simply too expensive for all but the tiniest fraction of the market; you could buy a pair of lower-end chips (from Intel or AMD) and beat the 3175X out that way if it was priced too high. At $3,000, the chip can argue to offer some overall performance advantages in workloads that can scale to reach the 28-core / 56-thread level. There are, to be sure, fewer and fewer workloads capable of taking advantage of this kind of capability the more cores you pack on the chip. Diminishing marginal returns, courtesy of Amdahl’s Law, absolutely kick in. But when it comes to a CPU this powerful, chances are you either know you can use it or know you can’t.

Continue reading