On Apple Silicon Macs, the RAM is shared. So while maybe not up to raw GPU VRAM speeds, it still manages over 450GB/s real world on M4 Pro/Max series, to any place that it is needed.
They all do have a limitation from the SSD, but the Apple SSDs can do over 17GB/s (on high end models, the more normal ones are around 8GB/s)
Yeah, I am mostly only talking about the SSD bottleneck being too slow. No way Apple gets 17GB/s sustained. SSDs thermally throttle really fast, and you have some random access involved when it needs the next expert.
They all do have a limitation from the SSD, but the Apple SSDs can do over 17GB/s (on high end models, the more normal ones are around 8GB/s)