The first Macs powered by Apple-designed processors are finally here. And from the outside, they’re almost dead ringers for the Intel-based Macs they’re replacing.
But on the inside, they’re not like other computers. Apple has brought its approach to system design, learned through years of iteration on the iPhone and iPad, to the Mac for the first time.
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Those of us who are used to thinking of personal computers in certain terms are going to need to adjust to this new reality. It’s a world in which Apple sells three different Mac models without even disclosing the clock speed of the processor inside. (It doesn’t do it for the iPhone or iPad, after all.)
But perhaps the item on the spec sheet that will require the biggest diversion from the old way of thinking is system memory. It’s a feature that’s already frequently misunderstood (and frequently confused with storage size), and now Macs with Apple silicon are using it in an entirely different way.
The old way of thinking of RAM is dead. Welcome to the world of the Unified Memory Architecture.
Part of the package
Like Intel chips with integrated graphics, the M1 chip includes a graphics processor, and system memory is shared by both processor cores and graphics cores. (And also, in the M1’s case, the cores that make up the Neural Engine.) But in shifting its terminology to describe a unified memory architecture, Apple’s trying to point out that the M1’s approach is a bit different.
The biggest difference is that in the M1, the memory is a part of the M1 architecture itself. There’s no memory slot or slots on the motherboard of an M1 Mac, nor is there an area where a memory chip has been permanently soldered on. Instead, the memory is integrated into the same package that contains the M1 itself.
What this means is that when you buy an M1-based Mac and choose a memory configuration, that’s it. There have been many other Macs with soldered-on memory that couldn’t be upgraded, but this is a little different, since the memory is basically part of the M1 package itself.
Looking at the first round of M1 Macs, it seems that the M1 is only capable of using 8GB or 16GB of memory. That may not actually be a hard limit—perhaps Apple is holding back in order to limit these low-end systems. But it’s more likely that we won’t see Macs running Apple silicon with more than 16GB until Apple provides a higher-end variant of the M1.
Benefits of being unified
But Apple isn’t integrating memory into its systems-on-a-chip out of spite. It’s doing it because it’s an approach that can lead to some dramatic speed benefits.
The M1 processor’s memory is a single pool that’s accessible by any portion of the processor. If the system needs more memory for graphics, it can allocate that. If it needs more memory for the Neural Engine, likewise. Even better, because all the aspects of the processor can access all of the system memory, there’s no performance hit when the graphics cores need to access something that was previously being accessed by a processor core. On other systems, the data has to be copied from one portion of memory to another—but on the M1, it’s just instantly accessible.
These new Macs are, in their way, kind of alien. The tradition in personal computers was that everything was modular, an outgrowth of the early PC era. Even though the Mac never participated in the build-a-PC ethos, the parts Apple used to assemble Macs came from that industry. Compare that with the smartphone, where Apple has continued to integrate more portions of the system into its single processor package in order to increase efficiency. These new Macs are far more like smartphones than like traditional PCs.
Do you need it?
One of the biggest criticisms I’ve seen about this first round of M1 Macs has been that they just don’t offer enough memory, maxing out at 16GB. Keeping in mind that these are the lowest-powered Mac models, it’s likely that future models will offer more RAM options.
But it’s also worth considering just how squishy the need for more memory can be when you poke at it. Sure, a lot of people feel they need it—but do they, really?
Yes, when a Mac runs out of physical memory, it will page the contents of memory to disk—and even super-fast SSDs are slower than main memory! Though the speed differences are a lot less than back when we used slow spinning disk drives.
What would cause your Mac to run out of physical memory? If you leave an awful lot of apps open at once, or if your browser has hundreds of tabs open, or if you’re using an app that loads a very large file (like, say, a Photoshop file) into memory. If you’re someone who does this a lot, you probably want more memory…. but then again, if you’re someone who does this a lot, you might not want to buy one an M1 Mac right now. The mid-range and high-end models that will undoubtedly offer more RAM options and more processor power are undoubtedly coming next year.
But if you combine the efficiency of the unified memory architecture with the speed of SSD storage, and consider most everyday use cases, I’m pretty sure that most regular users could get by with 8GB of unified memory—or, if you want to be absolutely sure, upgrade that to 16GB. (I did.)
I can’t imagine 2021 passing without Apple rolling out a new set of Macs with more powerful processors and more memory options. The high-end MacBook Pros and the iMacs, at the very least, could use updates that provide some options beyond the basic M1.
In the long run, is it possible that Apple would build systems with external graphics processors with their own dedicated memory? It seems inevitable, at least at the high end—what’s a Mac Pro for if you can’t stick a ridiculous graphics card in it?
But Apple is also very likely to just keep scaling up memory options as it scales up its processors, adding more memory as it adds cores—and those chips are the ones likely to be offered in most Mac models.
The unified memory architecture in the M1 is one of the reasons these Macs are so amazingly fast—but all Mac users are going to have to relinquish some of our assumptions about how our computers work, and how they’re configured. And if you really can’t bear buying any Mac with only 16GB of RAM, don’t get mad—be patient. More Apple silicon Macs are on the way.