Craig A. Hunter


2019 Mac Pro (28-core) Review

“In closing, I would like to say that, as far as students and teachers, scientists and engineers, everyone having this supercomputer power, desktop power – I’ve been waiting a lifetime for this, or maybe two lifetimes.”

Those were the words of the late Richard Crandall, former head of Apple’s Advanced Computation Group, on August 31, 1999 when he was on stage with Steve Jobs and Phil Schiller at Seybold San Francisco. They were introducing the Power Mac G4 that day, and the notable breakthrough was that it brought gigaflop CPU performance to a desktop computer for the first time. Back then, scientists and engineers usually had to buy supercomputer time (at about $1000/hour) to get gigaflop performance, so having it on a desktop computer was a big deal.

Just over 20 years later, the new Mac Pro has achieved a similarly impressive feat, bringing teraflop CPU performance to a desktop Mac. Sadly, Richard isn’t around to see it, but I am sure it would have pleased him immensely. One of these days I need to write about the fun work I did with Richard on vectorization and numerical methods, but today we’re going to talk about the new Mac Pro.

Apple was kind enough to lend me a 28-core Mac Pro, decked out with a 2.5GHz Intel Xeon W (turbo boost to 4.4GHz) having a single 38.5MB L3 cache, 1MB L2 cache per core, 384GB of 2933MHz DDR4 ECC memory, a 4TB SSD, and two AMD Radeon Pro Vega II Duo 2x32GB graphics cards (each with two GPUs, for a total of four GPUs). Priced out on Apple’s website, this configuration goes for an eye-popping $31,199 ($10,800 of that is for the GPUs alone).

The first thing that jumped out at me when unpacking the Mac Pro was its weight – at nearly 40 pounds, it’s a monster. Once I got it out of the box and onto my floor, I was struck by the beauty of the stainless steel and aluminum case. Now, having spent time working in a machine shop during my younger days, I’m probably not normal since I see elegance and wonder in a hogged out piece of aluminum. But the multiple tools and plunge angles that were needed to make a complex 3D lattice out of solid aluminum is impressive to me, and I think even a normal person would marvel at the case design. It’s striking, and it says “Pro” like no other computer I’ve ever encountered. Even the thick 15 amp power cord, which has the heft and feel of welding cable, looks and says pro.

The monstrous weight and visual impact of the Mac Pro is matched by its performance. Right out of the box, I ran a LINPACK benchmark and saw over 1.5 teraflops of CPU performance. For comparison, that’s over 55% greater performance than the 18-core iMac Pro I reviewed in 2018. Results are shown below. For this test, the LINPACK benchmark solved a dense system of 15,000 linear equations (by LU decomposition with partial pivoting, for you Richard Crandalls out there) using Intel's Math Kernel Library benchmark code. Whereas the iMac Pro tops out at 970 gigaflops with all 18 cores, the Mac Pro surpasses that level with just 13 cores and goes on to top out at 1.5 teraflops on 28 cores.

Next, let's look at an engineering benchmark, using computational fluid dynamics (CFD) for aerodynamic analysis. For this work, I used the USM3D CFD solver available from NASA to study flow over the ubiquitous NACA 0012 airfoil shape. Results show USM3D hitting 62 gigaflops using all 18 cores on the iMac Pro. The Mac Pro passes that level with 11 cores and runs up to 88 gigaflops on 28 cores -- a 42% increase in performance.

To close, I want to show a real-world application of CFD where a machine like the Mac Pro can have an impact in a daily workflow. In the fields of architectural aerodynamics and wind engineering, we study the effects of wind on buildings and structures, often looking at loads and effects on designs, materials, and even fasteners. One particular study I did a few years ago involved analyzing the uplift loads due to hurricane-force winds acting on different types of open roof structures (open roofs could represent marine structures, pole barns, picnic shelters, etc). Example results are shown below for a 100mph wind coming in at a 30 degree angle from the left, as it flows over a 4:12 closed gable roof.

Now, ordinarily these computations are run on a supercomputer and cost thousands of dollars per solution, or you’d need to build a cluster for $15-20K or more. But with 28 cores and the ability to handle up to 1.5TB of memory, the Mac Pro is a competitive alternative. To test that, I ran a wind simulation case on the Mac Pro and was able to obtain a converged solution in just 42 minutes, which puts the Mac Pro in a very productive club and justifies the high cost of the machine. A $20-30K Mac Pro doesn’t make sense for very many computer users, but an engineering firm would get their money’s worth out of the machine in short order.

While running this test, all 28 cores were pegged at 100% for the full 42 minutes, but the Mac Pro’s fans never got loud, airflow never got excessive, and temperature stayed comfortable. The Mac Pro operated with a very quiet low frequency whoosh that is leagues ahead of similar workstations I have used, and would be well suited to an office environment. I can remember running similar cases many years ago on a quartet of 2012 Mac Pro machines that were insanely loud and required a window air conditioner to keep my office temperature below 85°F, in winter no less!


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