Know Your Processors: Intel Core and Xeon

20 Nov, 2014 By: Alex Herrera

Herrera on Hardware: A primer on workstation CPUs for CAD.

More cores per CPU. While both Xeon and Core are built around the same CPU core microarchitecture, Xeon allows the option to configure systems with many more processing cores. Why does core count matter to CAD professionals? In the age of multicore computing architectures, the more processing cores that are available to work, the more quickly the work gets done. Common CAD tasks such as finite-element analysis (FEA) and computational fluid dynamics (CFD), for example, tend to multi-thread well.

A multitude of cores can help run one application or execute a single task more quickly, but it can enable a more powerful work paradigm for the ultimate multitasker: the professional who's using that computing power. The more computing cores you have at your disposal, the more you can unleash your own parallel-processing ability to keep more plates spinning at once, such as running a structural integrity analysis while kicking off a high-quality rendering, or modeling a wing while simulating airflow for turbulence. By harnessing as many as 12 cores in Intel Xeon E5-2600 v2 series CPUs — twice as many as the high-end Core brand processor — designers can shorten each workflow task and juggle more tasks at one time.

Cache and other features. Intel typically pairs more L3 cache (level 3, or shared internal chip memory) with its Xeon CPUs than with its Core CPUs. At 30 MB, the E5-2600 v2's L3 cache dwarfs the largest Core CPU's cache. Well-suited to handling the bigger data sets that CAD professionals employ, a bigger cache means fewer off-chip memory accesses, reduced latency, and higher overall throughput.

For the most demanding CAD users, Xeon's appeal for compute- and memory-bound tasks isn't limited to single-socket configurations. Xeon E5 supports configurations with two CPU sockets, and twice the number of processors in the system means twice as many cores. A dual-socket workstation with a 12-core Xeon E5-2600 v2 yields 24 cores, a full four times more than what a Core brand workstation can provide.

The benefits of dual sockets don't start and end with maximum core counts. With both memory and I/O now directly connected to each CPU in Intel's system architecture, adding a second Xeon CPU immediately doubles (or more) the maximum memory size, available memory bandwidth, and I/O bandwidth. A dual-socket workstation motherboard that houses two Xeon E5-2600 v2 series CPUs can support up to 768 GB of memory, supported by four memory channels delivering 59.7 GB/s.

Compare that with a top-end Core i7 CPU that maxes out at 32 GB, with two channels providing 25.6 GB/s. And, with more available I/O lanes, a dual-socket Xeon machine typically can accommodate more PCI Express add-in cards than a single-socket platform — as many as four graphics cards, for example. Too often, the performance metrics that garner attention are limited to GHz, MIPS, or FLOPS, when in practice, throughput is frequently bottlenecked by memory footprint, bandwidth, or both.

Error-correcting code. A PC gamer might sacrifice reliability for a few more frames per second, but a CAD professional can't afford any downtime — there simply is no substitute for dependability. Reflecting those priorities, Xeon offers error-correcting code, a memory technology that can detect and correct single-bit errors in memory. Bit errors in memory are not commonplace, but they occur more often than you might think. A Google-commissioned study, "DRAM Errors in the Wild: A Large-Scale Field Study," found that "about a third of machines and over 8% of DIMMs ... saw at least one correctable error per year." After comparing the modest price premium of ECC-capable memory to the potential cost of an uncorrected memory error — in lost labor, slipped schedules, or erroneous simulation results — more than a few work-station buyers justifiably opt for Xeon CPUs.

Xeon v. Core: Key Differences

The CPU Matters

A strong, strategic reentry by AMD CPUs in the workstation space would increase competition and be a welcome change for workstation suppliers and their customers. Still, as the only CPU supplier currently focused on this market, Intel provides highly capable processors to power workstations, carrying two different product lines to meet the range of needs of CAD professionals. Both tap the same foundation of CPU technology, but they're designed to meet different needs. Core products focus on single-thread performance, while Xeon picks up where Core leaves off, providing maximum reliability and substantially higher performance, particularly for multithreaded applications dealing with larger data sets.

Which is right for you and your workflow? If you're dealing with smaller designs such as consumer products and you're on a tighter budget, Core will suit your needs. But, if you're up to your eyeballs in big design projects — automotive or aerospace, for example — regularly running complex FEA or CFD simulations, and can't tolerate the slightest risk of downtime, you'll want to give the added capabilities of Xeon a good, long look.

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About the Author: Alex Herrera

Alex Herrera

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