The much-anticipated 2023 Mac Pro will almost certainly lack features considered critical for workstations: upgradable RAM and support for eGPUs. But this isn’t Apple blindly making an error — it’s an inescapable fact of the M-series’ unified memory architecture.
The limitation isn’t new: it’s been known since the M1 processor was announced. But the imminent release of a top-tier macOS workstation is shining a spotlight on the problem.
For those who weren’t paying attention back in 2020, here’s an explanation of why RAM upgrades and plug-in GPU likely aren’t an option for the 2023 Mac Pro.
Graphics professionals expect RAM upgrades and eGPUs for workstations
Consumers like high-end computers — a faster computer is easier to use. But graphics professionals absolutely require the most performance they can get. Rendering large amounts of high-resolution 3D animation takes powerful computer resources. Slow computers can be the difference between a profitable video production company and bankrupcy.
A graphics workstation requires a blazing-fast processor, of course. But a truckload of RAM is necessary too, and maybe an eGPU, too. Which is why it’s such a problem that the 2023 probably won’t offer user-upgradable RAM or eGPU support.
It’s a lesson Apple learned the hard way. The 2017 iMac Pro lasted for a mere three years of lackluster sales before being discontinued, partially because RAM upgrades required an expert to disassemble the computer. Compare that to 2019 iMac Pro — upgrading its RAM is as easy as plugging in the chips. Adding an eGPU to that computer is just as simple. But that workstation uses an Intel processor, not Apple silicon. And Cupertino may have set itself up to repeat the mistakes of the iMac Pro in its next workstation.
Understanding the Mac unified memory architecture
Understanding why 2023 Mac Pro RAM and GPU upgrades might be impossible requires diving into the M-series’ unified memory architecture. As Apple put it back in 2020 when the first M-series chip launched, “Macs and PCs have traditionally used multiple chips for the CPU, I/O, security, and more. Now with M1, these technologies are combined into a single SoC, delivering a whole new level of integration for greater performance and power efficiency.”
In somewhat less technical terms, the M1 and M2 are more than simply a Central Processing Unit. The Graphics Processing Unit is also built in. As is the RAM. These are all integrated parts of the System on a Chip.
It’s the secret to the extremely fast performance of the M series. Data moves more quickly between the components built into the chip that it can between separate processor, RAM and GPU chips. Plus, the unified memory architecture “allows all of the technologies in the SoC to access the same data without copying it between multiple pools of memory, further improving performance and efficiency.”
The weakness of the architecture is that individual components can’t be upgraded. It’s not possible to add more RAM to the SoC, or swap out the GPU.
While it’s theoretically possible to add more RAM off the chip, this would not take advantage of the significant speed boost that comes from memory built into the chip. In short, this add-on RAM would slow down performance, the opposite of the reason why it’s being added.
The same problem affects external graphics processing units, called eGPUs. Apple used to sell these for Intel-based Macs but has since stopped because they aren’t compatible with the M series.
Perfect for MacBook but bad for Mac Pro
To be clear, the unified memory architecture isn’t flawed. It’s what allows Apple to offer MacBooks with excellent performance paired with long battery life. And MacBooks make up the lion’s share of Mac sales.
The challenge is that battery life is immaterial to workstations. They need maximum performance. And while that means the M-series isn’t well suited for top-of-the line professional desktops, that’s a niche business.
Apple surely made that calculation when it adopted the M series. It picked the option that benefited the most users.
Is there a solution for the 2023 Mac Pro?
Cupertino had to know the unified memory architecture was going to be a problem for its workstations long before the M1 was unveiled. But there’s no simple solution — the difficulty is built into the processor.
One option is to keep using Intel processors, but that comes with its own drawbacks. An inability to make a chip worthy of a workstation will be taken by critics as proof that Apple silicon is inferior to Intel. Also, Cupertino surely hopes to be able to stop developing macOS for Intel processors some day — that won’t be possible if it continues to introduce new Intel-based Macs.
Another option, and the one Apple is most likely to pursue, is making M-series processors for the 2023 Mac Pro preloaded with tons of RAM and a very high-speed GPU. We may already know about what’s in development: leaks indicate the upcoming M2 Ultra chip will feature 24 CPU cores, a 76-core GPU and 192GB RAM. However, Apple might have nixed a rumored M2 Extreme configuration that would have come with 48 CPU cores, a 152-core GPU and up to 384GB RAM (a pair of M2 Ultras grafted together).
Whether these heavy-duty, non-upgradable processors will satisfy graphics professionals won’t be known until we find out how the 2023 Mac Pro performs in the real world. We could have that answer as soon as March.
