Unified memory
Quick answer
Unified memory is the single pool of RAM in an Apple silicon Mac, shared by the CPU, the GPU and the Neural Engine. There is no separate graphics memory: what the GPU uses comes out of the same 8, 16, 32 or more gigabytes as your apps.
On an Intel Mac with a discrete graphics card, the card had its own memory and the Memory tab in Activity Monitor never saw it. On Apple silicon the GPU draws from the same pool, so a game, a video export or a machine learning model shows up in Memory Used, Wired Memory and, when it runs out, in Swap Used.
The upside is that data does not have to be copied between the CPU and the GPU, which is part of why these Macs are fast. The cost is that memory pressure is shared: a heavy GPU task can push app memory into swap, and a Mac full of browser tabs leaves less for the GPU. Unified memory is soldered to the chip and cannot be added later.
How unified memory shows up in Activity Monitor
Open the Memory tab. Memory Used counts everything in the pool, including what the GPU has claimed, and Wired Memory grows during GPU work because those pages cannot be swapped out while the GPU holds them. The GPU History window shows the load but not the memory it uses, and no column attributes GPU memory to a process.
The Memory Pressure graph at the bottom is the figure to read. Green means the pool is coping, whatever Memory Used says. Yellow and red mean macOS is compressing and swapping to keep up, and a GPU task is a common cause on 8 and 16 GB Macs.
How much unified memory you need
Watch Memory Pressure over a normal day. If it stays green, you have enough. If it turns yellow during the work you do most, the next Mac needs more, because this one cannot be upgraded. Swap on an Apple silicon Mac's SSD is fast enough that yellow is usually fine and red is the sign of trouble.
Local AI models are the new reason to want more: a model has to fit in memory to run, and it shares the pool with everything else you have open.
- 8 GB: mail, web, documents and light photo work, with swap doing some of the lifting.
- 16 GB: most people, including development and moderate video and photo work.
- 32 GB and up: large video projects, virtual machines, many containers, or local AI models.
Questions people ask
Is unified memory the same as RAM?
Yes. It is the Mac's RAM, named for the fact that the CPU and the GPU share it. When a Mac's specifications say 16 GB of unified memory, that is the whole memory of the machine, not an addition to it.
Does the GPU use unified memory?
Yes, and that is the point of the design. Whatever the GPU holds comes out of the same pool your apps use, and it shows in Activity Monitor's Memory Used and Wired Memory while the GPU work runs.
Can I add memory to an Apple silicon Mac?
No. The memory is part of the chip package and is fixed when the Mac is built. Choose the amount when you buy, using Memory Pressure on your current Mac as the guide.
Related
Step by step: How to free up RAM on a Mac.
Want to watch this all the time? See the best system monitors for Mac, or the best Activity Monitor alternatives. Or browse every term in the glossary.