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Melatonic | on: Launch HN: Discovered Materials (YC P26) – AI agents to discover new materials
Love your idea of HBM on top of the chip. I've been saying for years that limiting memory to the edges is going to be an inherent physical limiter. I think the only reason it hasn't become more of a thing is that chip size has also been increasing with increasing compute.

What about HBM on the back side of the chip ? Essentially I'm thinking like a soldered on piece or another "socket" with pins like a CPU in the back of the motherboard. We rare see cooling elements there already and while most rack mount cases are not at all designed for more space there I don't see why it couldn't be a thing. Especially with liquid cooling.

Also makes me think of possibly using Gallium Nitride instead of silicone for surface levels elements ? Or maybe even an interface layer on top or bottom of the chip designed to be able to transmit power with less heat. Maybe that could be sandwiched between the chip and HBM.

akashramdas | parent
oh that's a very interesting question! -- HBM on the back side of chips has advantage and disadvantges. Logic atop HBM means power delivery becomes the bottleneck. This is equally problematic. My understanding is that the industry seems to prefer HBM on logic currently. Also for the bonding, I think we are going to see hybrid-bonding very soon! Instead of solder, we can directly connect the indivdual dies.

I think the switch to GaN is already happening for power, but Si is considered better for logic dies like the GPU. Also GaN is worse thermally than Si so the problems are actually amplified