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HBM4 has over 2048 signals to the processor’s PHY with tight signal integrity requirements that require the HBM stack to be < 0.5 mm from the processor die. Tha
by craigjb 13d ago
HBM4 has over 2048 signals to the processor’s PHY with tight signal integrity requirements that require the HBM stack to be < 0.5 mm from the processor die. That’s why HBM integration is done with interposers (soldered on the package). So, it’d be the CPU package that integrates it. Motherboard is too far away.
- Melatonic 13d agoKind of seems like we should be making chips with both. Big HBM stack on top as a sort of huge L5 cache like thing. And then a bunch of DRAM type sockets (like LPCAMM) around the exterior.
- craigjb 13d agoFor chips with integrated CPU+GPU+NPU, it could be worth it tech-wise. The GPU and NPU can eat HBM bandwidth. For general purpose CPU code, the HBM would likely not be worth it. It's high bandwidth, but you trade latency, and general CPU code is branchy. Economics-wise, the HBM stacks alone will cost more than a consumer CPU (or APU). [edit] The packaging needed to support HBM is also much more expensive too. If demand for current HBM applications tanks and the manufacturing lines need filled, then maybe. Currently, the price point would make it very very niche.