Reiner Pope

Yeah, I mean, let's sort of zoom in on this and look at the wire density.

I'll draw this diagram just once more so we have a bit of a cleaner version to work with and a larger version.

Let's say I have some switches in the middle.

And let's say I'm going to have, initially I'm going to start with just two GPUs on each side or two trays of GPUs on each side.

And let's say maybe each tray wants to have two cables coming out of it.

So I get some kind of, I physically run vertical cables that look like this running onto the switches.

Now, if I want to double the number of GPUs in a rack,

I need to run like literally twice the density of cables.

So I need to run these as well.

Yeah, so there is space outside the rack.

Inside the rack, like these racks are like, I mean, as they become more optimized, these racks are very tight.

So there's connector density going from the tray into the rack and the rack's backplane.

And then the backplane itself has a really high density.

There are other physical constraints, including bend radius of cables.

You don't want to snap them and so on.

Yeah, so rack design is not my expertise, but when I talk to folks on what are the constraints they're up against, it's a combination of what are the big physical things you're optimizing for,

Space, weight of the rack, like it's actually really heavy.

And so like you need enough metal top to not sag and fall.

But then you add more metal and it's heavier.

And then power and cooling.