Intel’s Comet Lake-S Rumored to Pack 10 Cores, Debut on 14nm

Intel’s Comet Lake-S Rumored to Pack 10 Cores, Debut on 14nm

In the wake of Intel’s latest Core i9-9900K launch, there have been questions about just where the CPU market would go from here. As things stand, both AMD and Intel have rolled out eight-core/16-thread chips at the top of the desktop market. Both companies are working on die shrinks and architectural improvements for their next round of products, but AMD’s 7nm Epyc demonstrations at New Horizons showed that the company has kept the same number of cores per die that it deployed with first round of 14nm hardware: Eight cores per chiplet, possibly split into two CCXs of four cores each (though this point is unconfirmed). Now, however, there are rumors that Intel might try to bump core counts northward again, with a 10-core part supposedly debuting on a 14nm Comet Lake-S CPU in 2019 with a dual ring bus.

I want to make it clear that this rumor, sourced from a Taiwanese forum, should be taken with a huge pile of salt. Intel has used a dual ring bus for its high-end Xeons before, typically in configurations like the below. More recently, it has shifted to a mesh network for its high-end multi-core CPUs. Coffee Lake currently uses a single ring bus interconnect. Moving to a dual ring bus for a 10-core chip as opposed to a mesh network would imply Intel is creating some differentiation between its Core X/Xeon family of products and its desktop chips. Other aspects of these CPUs remain entirely unknown, including any question of architectural enhancements or additional hardware fixes for the speculative execution issues that continue to surface.

Intel’s Comet Lake-S Rumored to Pack 10 Cores, Debut on 14nm

The larger question, again assuming that this rumor is accurate, is exactly how many cores we’re going to see Intel and AMD try to bring to desktops in the first place. While multi-threaded applications are far more robust than they were 10 years ago, it’s not unusual for standard desktop apps to show relatively little scaling above four cores. Even apps that do scale above four cores/eight threads tend to show diminishing returns for adding new CPUs. There’s also an associated power cost with higher core counts and it’s harder to hit high frequencies. Intel’s Core i9-9900K manages to hit a 5GHz boost clock, but overall power consumption is higher than its predecessors courtesy of the increased core counts.

Some might argue that this is simply a retread of the ancient “Do you need a PC this fast?” argument that typified reviews of an earlier age, but such comparisons are misguided. First, the rate of absolute improvement in CPU performance today is literally an order of magnitude smaller than it once was, at least. Second, Amdahl’s law tells us that there’s a hard limit to how much performance can be improved in any given application by adding more CPU cores. Serialized code inevitably becomes a bottleneck. Intel CPUs tend to be less sensitive to memory bandwidth than their AMD counterparts, but adding more cores without increasing the total amount of memory bandwidth in the system will eventually impact CPU scaling as well. Whether that happens at the 10-core point isn’t something we can speculate on without testing, and there are cache techniques that can alleviate this impact to some extent, but it’s definitely something to be aware of.

Data from Steam Hardware Survey
Data from Steam Hardware Survey

It’s good to see the CPU market moving forward in terms of core counts, but we’ve seen core counts offered at a given price point jump dramatically in just the past two years thanks to AMD’s Ryzen processor. The market has definitely noticed — the number of CPUs with more than four cores has grown substantially in recent months according to the Steam Hardware Survey — but dual-core and quad-core chips still hold ~88 percent of the market. Rumors that the PS5 and Xbox Next will use Ryzen-derived 8-core chips could mean the next generation of games will lean more on CPU horsepower and respond better to higher thread counts, but strong multi-threaded adoption in games has played out slowly over years.

But diminishing returns are inevitable as core counts increase, particularly when they leap ahead quickly. This is not to say that a 10-core Comet Lake won’t deliver improvements over the Core i9-9900K, but that buyers of this still-hypothetical part will want to pay careful attention to where it does and does not improve overall performance. If this part is real, it also implies that Intel’s initial 10nm push will focus on mobile and low-power systems, similar to how the company rolled Broadwell and first-generation 14nm as a mobile solution first and foremost. While not impossible, it seems unlikely that Intel would launch a 10-core 14nm part on desktop next year, only to turn around and drop 10nm silicon in the same space.

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