Professionals have eagerly awaited an updated version of the Mac Pro workstation that uses Apple silicon, instead of Intel CPUs. The ability to scale Apple silicon to compete with Intel’s premium Xeon processors has been a recurring talking point among industry watchers and prospective buyers, who have deferred purchases of Mac Pro workstations in hopes of maximizing their investment. As the expected service life of a Mac is generally longer than those of comparable PCs, and the service life of enterprise-grade workstations is longer than those of consumer devices, anticipation has been building since Apple announced the transition of the Mac to Apple silicon at its Worldwide Developers Conference (WWDC) in 2020.
Apple’s introduction of the M2 Ultra for the Mac Pro and Mac Studio at WWDC 2023 completes this transition. Shifting other Mac products from Intel CPUs to Apple’s “M” series silicon has been a success, with Apple receiving plaudits for performance, battery life and the Rosetta 2 application compatibility layer.
Often, the focal point of Apple’s silicon shifts is the instruction sets — moving from x86-64 to AArch64 isn’t trivial. But the adoption of unified memory architecture (UMA), with the processor chipset and RAM mounted together in a system-in-a-package design, is as important, if not more so, for the performance gains in Apple silicon. Although this integration is a benefit for portable and low-profile devices like the MacBook, iMac and Mac mini, it presents a challenge for the Mac Pro workstation, because expandability is one of the things that sets it apart from other Mac products.
Apple’s solution for this is the M2 Ultra — essentially, two M2 Max chips combined using a silicon interposer. It’s the same strategy found in the M1 Ultra, which debuted with the Mac Studio in 2022. Each configuration of the M2 Ultra is available in the new Mac Pro and Mac Studio, with the Mac Pro including six PCI Express (PCIe) slots. Viewed from one angle, that makes the Mac Studio tremendous value: top-line performance without the added expense of a full Mac Pro. From another angle, it raises the question of why professional users would need a Mac Pro when the Mac Studio offers equal levels of performance.
Performance Improvements in the M2 Ultra in the Mac Pro and Mac Studio
The performance is itself noteworthy — as I’ve mentioned in a previous blog post, and as Apple executive Jennifer Munn noted in the WWDC presentation, the UMA design allows developers to train and infer against large language models such as Meta’s 65 billion-parameter LLamA model without relying on cloud services. This isn’t possible today with the same size models on other developer workstations, as GPUs aren’t equipped with comparable amounts of RAM. Likewise, for 3D modelling, the ability to edit complex models is a similar benefit.
This isn’t frictionless, however. Development work is needed to remove dependencies on Nvidia’s CUDA technology, which is firmly entrenched in artificial intelligence and graphics. In 3D modelling, OTOY’s Octane, Maxon’s Redshift, and Blender Cycles and Eevee all support Apple’s Metal graphics API, although Pixar’s RenderMan XPU does not. Apple introduced its Game Porting Toolkit at WWDC to aid developers in porting games for Windows to MacOS. Similarly, model developers rely on Apple’s coremltools to convert machine learning models to Apple’s Core ML format.
Although these advancements in software are welcome, Apple will need to continue investments in its APIs and developer tools as well as open-source software and frameworks to aid third-party developers in usefully exploiting the capabilities of the hardware.
The Utility of Expansion in a Tightly Integrated System
The meaning of “Pro” in Mac Pro has been the subject of speculation throughout the transition to Apple silicon. The M2 Ultra, although formidable, isn’t an Intel Xeon — the two chips are difficult to compare, as they represent fundamentally different approaches to building a processor. Still, the 2023 Mac Pro is the first not to have user-replaceable RAM or a socketed processor, limiting potential upgrades. On specifications alone, the M2 Ultra Mac Pro does not compare favourably, providing a maximum 192GB of RAM, compared with a maximum 1.5TB for the previous Intel model.
Realistically, practical deployments of Mac Pro units with 1.5TB of RAM are few and far between, as the big data workloads that typically require these capacities are more likely run on Linux, typically on cloud platforms. Although it’s a compromise, a smaller amount of extremely fast RAM — 800 GBps on the M2 Ultra — provides more versatility for developers than a large pool of slower memory. (The 2019 Intel Mac Pro, when fully equipped, has a maximum RAM speed of 140 GBps.)
Although the new Mac Pro includes two PCIe 4.0 x16 slots and four x8 slots, they don’t support external GPUs. Ignoring stated incompatibility, the Mac Pro includes two six-pin power connectors providing 75 W each and one eight-pin power connector providing 150 W, falling short of the 16-pin, 320 W power delivery needed for current GPUs. The GPU in the M2 Ultra should eliminate the need for third-party GPUs, but the PCIe slots must provide some utility to justify the added cost.
That expansion is for the benefit of data processing. Apple touted the appeal of the Mac Pro for video production with systems equipped with Blackmagic Design DeckLink 8K Pro PCIe cards to ingest 24 4K camera feeds and encode them to ProRes in real time. Expanded storage is also an option, with Apple providing storage upgrade kits for the on-board boot drive, and third-party products such as OWC’s Accelsior 8M2 provide up to 64TB of SSD storage using one PCIe 4.0 x16 slot. These capabilities, as well as the rack-mountable variant of the Mac Pro, are a benefit to video production teams.
Choose Your Adventure
It’s very possible that mainstream workloads wouldn’t benefit from the PCIe expansion offered by the Mac Pro or could otherwise be served by connecting external hardware to Thunderbolt 4 ports. Seemingly, this is why the Mac Studio exists. For users planning to upgrade to this generation of Mac, not having to spend an extra $3,000 to get top-of-the-line performance is a substantial saving.
Conversely, it’s possible that a future Mac Pro provides more computing power than a future Mac Studio. The use of silicon interposers could allow four “M” series Max chips to be stitched together, which would be difficult to house in the current Mac Studio design. Although somewhat far-fetched, it’s possible that a future Mac Pro could use PCIe 5.0 and CXL to support tiered memory, to better support big data workloads.
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