Yeah, so DDR5 is 8GT and GDDR7 is 32GT. Bus width is 64 vs 384. That already makes the VRAM 4*6 (24) times faster.

You can add more channels, sure, but each channel makes it less and less likely for you to boot. Look at modern AM5 struggling to boot at over 6000 with more than two sticks.

So you’d have to get an insane six channels to match the bus width, at which point your only choice to be stable would be to lower the speed so much that you’re back to the same orders of magnitude difference, really.

Now we could instead solder that RAM, move it closer to the GPU and cross-link channels to reduce noise. We could also increase the speed and oh, we just invented soldered-on GDDR…

> Bus width is 64 vs 384.

The bus width is the number of channels. They don't call them channels when they're soldered but 384 is already the equivalent of 6. The premise is that you would have more. Dual socket Epyc systems already have 24 channels (12 channels per socket). It costs money but so does 256GB of GDDR.

> Look at modern AM5 struggling to boot at over 6000 with more than two sticks.

The relevant number for this is the number of sticks per channel. With 16 channels and 64GB sticks you could have 1TB of RAM with only one stick per channel. Use CAMM2 instead of DIMMs and you get the same speed and capacity from 8 slots.