From Howard Oakley at The Eclectic Light Company
If demands made on unified memory are more variable, and could require that a high proportion of physical memory is used for graphics and the display, this might result in increased use of virtual memory, and CPU cycles lost to caching. That was certainly a problem when caching to rotating disks, but with modern high-speed SSDs effects on performance are minimised. After all, an internal SSD is only larger and slightly slower-access memory. That requires tighter integration of internal storage too.
When I was a hardware tech at Apple I would often need to help customers understand the difference between RAM and storage. The most effective way of doing that was to liken RAM to your desk and storage to your bookshelf. However, this was during a time when most Macs still used platter hard drive. I wonder how true that analogy remains today – especially with the incredible SSD read/write speeds on machines with a T2 chip.
Speaking of T2 chips, I discovered Howard’s site while troubleshooting a (suspected) T2-related Kernel panic on my Mac mini. What an incredible repository of information. Truly one of the best Mac troubleshooting sites out there.