Yeah, it does seem like there's a fundamental limit how fast you can go even if you engineer the data juggling to perfection. My guess is that every loop through the transformer is going to have to visit every weight and if those weights cannot fit in your fastest memory, then it's going to have to spend time transferring data from SSD or whatever is lower in your memory hierarchy.

The quantization used in the post luckily seems to work somewhat well; I'm also wondering if some new clever ways will be invented that reduce the amount of data you need to juggle. Maybe e.g. not just using 4-bit weights but also compressing them in some way, sorting the weights or something.