Thanks @EricRFMA, @Shamino and all - very instructive discussions! From the links shared and further references in those documents, I am reading these to further understand how unified memory works (very complicated):
“Why Apple’s M1 chip is so fast” - discussion on CPU vs GPU memory requirements (low latency low throughput vs high latency high throughput) and how the UMA addresses these:
“Explore the new system architecture of Apple Silicon Macs” - with discussion of UMA:
Metal (GPU) memory management - shared, private and memoryless:
Clean vs dirty memory: