iMac Pro vs Mac Pro + eGPU

iMac Pro: Salvation after starvation?

Truong Nguyen Product Reviews

Today Apple released the highly anticipated iMac Pro. This marks four years since the introduction of the last pro Mac computer. The main selling features are the Radeon Pro Vega graphics card and the Xeon-W workstation processor, all packed in the thin and slick form factor of a 27″ 5K iMac. This beast of a machine starts at a whopping $4,999.

iMac Pro

iMac Pro

The iMac Pro is the most powerful production Mac to date. Apple claims pros love iMac so they went all in and built a “killer iMac.” They weren’t kidding around. You can buy an iMac Pro that’s equipped with an 18-core CPU and an 11-TFLOP Vega GPU. We have yet to see any information on thermal throttle and fan noise from such a machine. The 8-core and 10-core versions are the only ones available shortly after launch. The 14-core and 18-core options have a two month delay.

iMac Pro cooling system

There are reports of high fan noise and operating temperature on the 27″ 5K iMac i7-7700K + Radeon Pro 580 configuration. For the iMac Pro, Apple completely redesigned the cooling system for better thermal management. It will be interesting to see whether another thermal limit situation develops like in the late 2013 Mac Pro. The three processor options are a Xeon W-2145 8 Cores, Xeon W-2155 10 Cores, Xeon W-2175 14 Cores, or Xeon W-2195 18 Cores. Graphics card selections are a Vega 56 8GB, or Vega 64 16GB. The W-series Xeon CPUs are rated for up to 140W TDP, and Radeon Pro Vega GPUs are rated for up to 295W TDP. Apple of course needed to fine-tune (read underclock) these power-hungry components to accommodate the cooling system of the iMac Pro. We should all cross our fingers that the top-of-the-line configuration does not literally turn into an iMac killer from heat exposure.

Apple’s “pro” designation is interesting as of late. In my opinion this can be interpreted as 20% professionals, 80% prosumers and 100% proprietary. The internal images of the iMac Pro show the RAM modules may be swappable. Apple’s official confirmation is that the RAM won’t be user-replaceable. This means you may have to cut the glue and take the 5K display off in order to swap the RAM modules all while voiding the warranty. I’d like to see a teardown of this machine to determine upgrade possibilities.

Mac Pro

Let’s take a drive down memory lane of pro Macs in the past decade. The first generation Mac Pro is perhaps the most long-lasting Mac in recent history thanks in part to the conventional tower design that uses off-the-shelf computer components. Too bad it’s unlikely Apple will use non-proprietary parts in its next modular Mac Pro.

iMac Pro vs nMP Radeon Vega eGPU

The more recent Mac Pro, introduced all the way back in late 2013, is the trashcan-shaped object you see in the picture above. It was the highest performing production Mac until today. I have no engineering skills so my attempt at packing these powerful components behind a monitor to imitate the iMac Pro turned into a likely fire hazard. What’s on display is the Radeon Vega Frontier Edition GPU mounted in a modified AKiTiO Thunder2 that’s powered by a 500W ATX PSU and connected to the late 2013 Mac Pro.

As of macOS High Sierra 10.13.1 beta, the Radeon Vega graphics cards have drivers and native external GPU support. I’m currently running 10.13.2 [17C88] on the nMP. The Radeon Vega FE is working better than I expected, but there remain some issues. The cooling fan is running at a higher speed than in Windows 10, likely due to the borrowed cooling profile of the iMac Pro. The GPU identification is not detected correctly in About this Mac. It shows up as “RX XXX”. A simple hex edit to AMD1000Controller file helps with this cosmetic issue. When spring 2018 arrives, Radeon Polaris and Vega eGPU should work much better in macOS.

The Mac Pro 6,1 works not only with the DIY AKiTiO Thunder2 but also with many other Thunderbolt 3 eGPU enclosures to make use of external graphics. When paired with a Mantiz Venus and RX Vega 56 a few weeks ago, the experience was very much plug-and-play. Final Cut Pro X in particular got an excellent boost in performance. BruceX completed in about 24 seconds with the dual discrete D500s. Adding the RX Vega 56 eGPU nearly cut this time in half.

Another viable option to make use of the latest, most powerful graphics cards is with a Mac Pro tower (4,1 and 5,1). Even though it’s nearly ten years old, the Mac Pro tower has four standard PCIe 2.0 slots that allow straightforward installation of desktop graphics cards and peripherals. The two mini PCIe booster cables may not have sufficient power to handle the load of a Vega 64. Performing a pixlas mod to draw more juice directly from the PSU is highly recommended.

Closing Thoughts

The direction of Apple’s product portfolio is cause for concern if you prefer a headless Mac. The iMac lineup now starts at $1,199 with the base 21″ iMac and tops out at $13,348 for the top-of-the-line iMac Pro. This is a carryover from iPhone and iPad product offerings. It’s the same sausage, different lengths mentality from the auto industry.

The fact that Apple managed to shove all this power inside the footprint of a 27″ 5K display is an incredible engineering feat. The base model conveniently priced at $5K is marketing at its best. When a $1,000 iPhone can be replaced yearly on a payment plan, a $5,000 iMac Pro on a three-year lease is not far-fetched. Nevertheless, for those who want a powerful workstation that looks the part, Apple has answered their prayers. The success of this iMac Pro hopefully does not spell the end of the Mac Pro. For many long-time Mac users myself included, nothing short of a truly modular Mac would do.