CAD Tech News (#140)

Herrera on Hardware: AMD CPUs Check All the Boxes for the Range of CAD Computing Demands

The company's Ryzen 5000–generation CPUs solidify its resurgent competitive edge, particularly when it comes mainstream CAD.

By Alex Herrera

As I've touched on several times in this column, the era of multicore processors has not delivered universal benefits across all computing applications. That transition from a near-exclusive strategy of speeding execution of a single thread to one that accelerates aggregate throughput by deploying a multitude of processing cores to execute multiple threads in parallel has not been the tide that raises all boats. Among the most notable boats left behind are key workloads in CAD computing, which tends to exhibit more single-thread-limited code than many other high-demand computing applications. Parametric modeling, the cornerstone of many a workflow, is inherently sequential and not amenable to much speedup on more than one processing core.

That reality is one reason — though neither the only nor dominant reason — that Intel has held onto its position as the premier supplier of CPUs in the workstation and gaming segments of the market. The company has long managed, through both architecture and silicon manufacturing, to consistently deliver higher single-thread performance than its rivals, most notably including AMD. Also covered recently and often in this column, though, Intel's de facto monopoly on workstation-caliber computing is now being challenged — more aggressively and effectively than it has in over a decade — by a revitalized AMD riding the success of its Zen processor technology.

Still, the last of Intel's advantages to mitigate (and the one proving to be the most elusive) was the one that inordinately affects CAD performance: single-thread throughput. With the emergence of AMD's Zen 3 microarchitecture on the Ryzen 5000–generation CPUs, it appears that final advantage is finally ready to fall ... and in the process, should open the door even further to renewed acceptance for AMD CPUs for use in CAD environments.

Three Buckets of Workstation-Focused CPUs

For the purposes of this discussion, I'm going to lump workstation-caliber CPUs into three buckets, as a function of their core counts and clock frequencies. Here, it's worth remembering the inverse relationship of those two metrics: Driving one up pushes the other down, all else being equal. That relationship makes for an unfortunate reality for CAD users, as their workflows commonly employ some workloads that lend themselves well to execution on a multitude of cores and those that are inherently constrained to single-to-few-thread execution. (This inconvenient truth, and its impact, were explored in "Workstation CPU Cores and Clocks: An Inconvenient Tradeoff.")

All-out maximum core count, at the cost of reduced single-thread performance. This option is the biggest in physical footprint and power consumption, but it accounts for a very small volume of the market. This class of CPU accounts for only about 10–12% of fixed workstations (that is, not counting mobile workstations), and is currently dominated in the market by Intel's dual-socket-capable Xeon Scalable processors.

All-out maximum GHz. Harnessing more cores is a good thing, but only if it doesn't mean giving up much in the way of GHz — a metric that on the same architecture correlates to single-thread performance — to get those extra cores. In the past few years, that's generally meant quad-core CPUs are the sweet spot, though manufacturing progress (i.e., moving to denser 10-nm and 7-nm processes) has allowed that knee in the curve to transition to 6-core (6C) and eight-core (8C). That is, you can typically find a SKU with the highest base frequency (and usually, turbo modes as well) at 6C or 8C, so there's no need to opt for fewer cores.

What makes this CPU category interesting in the context of this column is that It's a popular bucket for many computer users, but perhaps foremost among them gamers and CAD users. Both are among the preeminent examples of computing workloads that are both highly demanding and frequently limited to single-thread execution.

The middle ground: heftier core counts, but without throwing in the towel on single-thread performance. For our third bucket, let's define a middle ground: those CPUs that sit in between, offering more cores than the baseline (again, call it 4–8C today), but not counts so large that users have to accept severe reductions in GHz in exchange.

AMD Aims to Offer Compelling Solutions for All the Buckets

The first box AMD ticked off was that top one: maxing out core counts. By tapping an approach to chiplet integration AMD calls the Infinity Architecture, engineers were able to stitch together two to several 8C silicon die, allowing for EPYC CPUs to scale up to 64 cores (for more information, see "Chiplet Architectures Emerge as One Arrow in Industry Quiver of Technologies Extending Compute Performance"). That core count eclipses Intel's current top-end second-generation Xeon Scalable line at 56 cores.

Stitching multiple 8-core "chiplet" die in a single CPU package lets AMD gracefully scale up to massive core counts. Image source: AMD.

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Alex Herrera is a consultant focusing on high-performance graphics and workstations.

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