I’m pretty sure it is not super relevant. The amount of vram in a GPU is different than the amount in a CPU. The system memory with x86 is mostly virtual bits. I haven’t played in this space in awhile, and so my memory is rusty. The system memory is not directly accessible by an address bus. It creates a major bottleneck when you need to access a lot of information at once. It is more of a large storage system that is made to move chunks of data that are limited in size. If you want more info read about address buses and physical/virtual buses: https://en.m.wikipedia.org/wiki/Physical_Address_Extension

In a GPU, the goal is to move data in parallel where most of the memory is available at the same time. This doesn’t have the extra overhead of complicated memory management systems. Each small processor is directly addressing the memory it needs. With a GPU, more memory usually means more physical compute hardware .

If you ever feel motivated to build vintage computing hardware like Ben Eater’s 8 bit bread board computer project on YouTube, or his 6502 stuff, you’ll see a lot of this first hand. The early 8 bit computer stuff is when a lot of this memory bus and address space was a major design aspect that is much more clear to understand because it is manually configured in hardware external to the processor.