February 17, 2022
Issue #156
The Misconception of Professional Computing and CPU Core Counts
Especially in CAD applications, lower core count CPUs still dominate the market.
It feels like I’m coming across the headline more often than ever before. Paraphrasing, the headline either states or implies that high core count CPUs — let’s roughly call that in today’s context as 10 cores or more — are dominating sales in the workstation market. On the surface, it’s an easy conclusion drawn from an accepted narrative. “High performance” CPUs are high-core count CPUs. And, since workstations are designed to deliver high performance then, of course, high-core count CPUs would logically be in high demand for both workstations and the top consumer of those workstations, CAD users.
The reality does not fit the headline, however, nor the simplistic narrative. The truth is that the median CPU among all workstations shipped in 2021 had only four cores. That’s worth repeating: in 2021, fifteen years after the introduction of the first quad-core processor, in the most (arguably) demanding segment in client-side computing, the typical machine still shipped with a quad-core CPU. Data on usage can’t be ascertained with precision, but I’d speculate that quad-core has been dominating sales in machines used for CAD at a higher rate than other workstation-relevant spaces. Only now, on the back of Intel’s 11th Generation Core (Rocket Lake, covered here) and 12th Generation Core (Alder Lake, covered here), are 6- and 8-core CPUs beginning to take over volume leadership. 2022 should finally be the year that the median moves up from the quad-core we’ve been stuck at for years.
The misconception is quite understandable, because on the surface, the narrative would appear to hold water. And indeed, in some segments of the market that rely on performance for heavily-threaded, parallel workloads, the premises leading to this conclusion are valid in some corners of the CAD world. The issue is that those corners of the CAD world represent a minority greatly outnumbered by the masses who focus their hardware choices on price/performance for mainstream CAD applications.
For Most CAD Workflows, Multi-thread Performance Still Takes a Back Seat
To be clear, yes, professional computing spaces like CAD are more likely to value and leverage as many cores as can be had, certainly a lot more than, for example, typical office applications and workloads. But no, it’s not the most common case for mainstream in those segments, where the most indispensable, time-critical tasks tend to leverage only a single thread of execution, or perhaps just a few (1T). Consider the universal, time-dominating iterative cycle of model, visualize, model, etc. Neither parametric modeling nor interactive 3D graphics processing effectively leverage a multitude of cores. (It’s worth emphasizing I’m referring to visualization via 3D graphics, not rendering, the latter of which can quite effectively harness many CPU cores. For a refresh on the significant differences in 3D graphics versus rendering, check out this previous primer.)
The Unavoidable Frequency Tradeoff
OK, but even if you’re one of the many whose computing productivity is still heavily dependent on 1T performance, what’s wrong with having more cores for the times you could take advantage of them? Consider tasks better suited parallel core execution, like physics and engineering simulations, and CPU rendering. Unfortunately, it can hurt because securing more cores isn’t free. It will cost you in two respects: dollars and frequency.
Consider the inverse relationship between core counts and frequencies this column has discussed in the past. As chips grow in size, the more power consumption concentrated on a single piece of monolithic silicon, the more difficult it is to dissipate the resulting heat and the bigger the die, the more difficult it is to maintain adequate signal integrity. Both challenges tend to tamp down the minimum guaranteed and sustainable clock rates (the base rate). I charted the base frequencies for the popular workstation CPUs both for mainstream, Intel’s Xeon W-2200 family, selecting the SKUs that represent the highest base frequency at the given core count. The decline in base frequency is clear, dropping from 4.1 GHz at 4C down to 3.0 GHz at 18C. So as core counts rise, we see that inverse relationship, where the minimum guaranteed operating frequency (the base GHz) declines.
The tradeoff presents another argument to forgo the higher core counts, assuming your primary interest is maximizing GHz to guarantee best possible 1T performance.
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