Apparently AMD patented something called "Infinity Cache"

Not enough to make a news Article since we only know that the patent exists, but there might be something of a big cache in the RDNA2.0 chip that has much, much higher bandwidth / latency compared to VRAM, and could explain why the rumored 6900 XT has a 256-bit bus (which normally would be waaaay to little memory bandwidth).

We'll have to see. If AMD managed to shove a good amount of "L4-ish" cache into their GPU and actually can leverage it in games this could be a way better innovation than Nvidia's "oh look, our INT cores can now do FP so let's count them as CUDA cores!" this gen.

All wild speculation at this point.