Radeon Pro Vega 56 vs. Vega 64: Which iMac Pro video card is better?

The iMac Pro comes with two Radeon Pro graphics card options. But which should you pick?

Despite its all-in-one nature, you can still customize most of your iMac Pro before it ever leaves the assembly line. Whether you want to upgrade your processor, RAM, storage, or accessories, Apple has a few options for you.

That includes graphics cards. While you still can't get an NVIDIA card (with all its CUDA glory) built into your iMac Pro, you will be able to choose from two of AMD's top-tier graphics cards: The Radeon Pro Vega 56, or the Vega 64.

Both cards are powered by AMD's Vega architecture, allowing for up to 11 teraflops of single-precision and 22 teraflops of half-precision computing. Add that to the Vega's High Bandwidth Memory (HBM2), and you'll be looking at higher frame rates on games, faster graphics rendering, and silky-smooth operation of the iMac Pro's 5K Retina P3 display.

Both cards will perform well for most users, but there are small tweaks that can benefit certain pros. Who should get each card? Read on.

Who should get the Radeon Pro Vega 56 with 8GB of HBM2 memory?

The Vega 56 is Apple's baseline card for the iMac Pro, providing full graphics power for Apple's 5K Retina display along with great performance in graphics rendering, high frame rate display for games, and more.

If you're interested in the iMac Pro primarily as a gaming or VR machine, the Vega 56 is an excellent card for those tasks, holding its own alongside the Vega 64 in most basic tasks. (You can see some specific benchmark data for the cards on GamersNexus, though keep in mind that this is in a build-your-own vacuum, and not tied to the iMac Pro's CPU architecture.)

That said, the Vega 56's 8GB of memory does limit it somewhat when it comes to more developer-focused tasks — 3D painting, VFX, video editing, and VR work. I asked iMore's VR expert Russell Holly to elaborate a bit about the card difference:

You're unlikely to see a massive difference between these two cards if all you are doing is gaming, but if you're using tools that tax the card in ways that are not actively shown on the screen at 90fps (as graphic artists/game devs tend to do) the difference is a great deal more substantial.

Visual artists/developers will see a significant performance difference between these two machines, but general consumers likely would not.

Those customers may immediately gravitate toward the Vega 64, instead, but there's also a third option: Apple's beta (soon to be standard) support for external GPU enclosures, or eGPUs.

In our interviews with developers during our first iMac Pro impressions, we heard from graphics artists who had chained multiple eGPUs to the iMac Pro to significantly boost its performance for visual-heavy tasks. It's a huge boon for professionals who want to work on a Mac but don't want to limit themselves to Apple's limited graphics architecture.

If you're largely planning to game on your iMac Pro or a pro who plans to buy eGPU enclosures for their work, consider sticking with the baseline Vega 56.

Who should get the Radeon Pro Vega 64 with 16GB of HBM2 memory?

Professionals who either can't afford eGPU enclosures or want the best combination of GPU power possible may well opt for the Vega 64, a $600 upcharge. Its extra HBM2 memory provides more freedom for those who work in graphics-heavy environments, while the increase in the graphics processor offers a slight uptick in performance, as well.

As upgrades go, the Vega 64 is one of the cheapest improvements you can make to the iMac Pro — and it's also an improvement that can provide a noticeable increase in functionality, should your work focus on graphics.

For a price comparison, your standard Thunderbolt 3 eGPU enclosure runs anywhere from $300-$500 (Mantiz's Venus runs $389), and you can pick up the Vega 64 card externally on B&H Photo for about $750. Pro-level NVIDIA cards are much the same.

You may well get better overall performance from buying an eGPU kit (or two) for your iMac Pro, but at a significant price increase; similarly, you might be able to get even better performance by pairing a Vega 64 and a single eGPU than going with the base Vega 56 and buying two (or more) eGPU enclosures.

If you're a pro who needs the extra juice the Vega 64 can provide — either because you don't want to buy an eGPU or you want to make the most of your computer and eGPU paired — you'll want to go with the Vega 64 chip.

Which iMac Pro graphics card would you buy?

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