3D V-Cache is basic bitch "3D". What I'm talking about could be connected thousands of times more densely than TSVs, with gigabytes of memory, ideally all of the memory your processor needs (e.g. 128 GB+), and possibly multiple layers of cores.
HBM is already doing this, just not hundreds of GB. Each HBM stack on an H200 is I think ~24 GB. Cooling's already an issue, though, and it has a high failure rate.
is it possible to stack transistors on top of each other on different layers of the same chip? How do they handle cooling then?
like say you had a four-core cpu that had each core sandwiched on top of each other, would it be impossible to cool it? or would there just be a max tdp it can operate at?
Heat can only leave the chip through the surface, so if you sandwich cores like that, the heat from inner cores has to pass through outer cores, causing a serious cooling problem, requiring some new, exotic technology. It might be more feasible with an all-photonics chip.
Unrelated: Since we were talking about servers, AMD just launched Turin, while Intel launched 6th Gen Xeon (Granite Rapids). It looks like Intel has finally gotten back to parity in server CPUs, as both companies' high-performance flagship CPUs have 128 cores.
They both also launched high-density solutions. Zen 5c and Intel E-Cores aren't strictly comparable, but those come in 192c and 288c versions, respectively.
Intel actually leapfrogged AMD in bandwidth this time, which is important to anybody running memory-bound workloads like engineering simulations or databases. Both Intel and AMD CPUs have 12 channels of DDR5 this goaround, but Intel supports DDR5-8000 MCR DIMMs, which multiplex two 64-bit channels into a single 128-bit channel.
AMD has been kicking ass in server chips since Zen 2, so I'm curious to see how the market responds to Zen 5 vs GR/SF. On paper, the latter is better.