EMIB Embedded Multi-die Interconnect Bridge
A small silicon bridge buried in the package substrate connecting two adjacent dies, instead of laying an entire silicon wafer underneath everything.
The alternative is a CoWoS-style interposer: a large piece of silicon that everything is mounted on top of. It works but is expensive, and it is limited by the same reticle size that governs manufacturing ordinary chips, which caps how big the package can get. Intel's solution is to put silicon only exactly where it is needed — a bridge a few square millimetres in size, embedded in the organic substrate beneath the boundary between two tiles, carrying the fine wiring that dense connections require. The rest of the package stays cheap substrate. The technique is used in Sapphire Rapids and combined with Foveros in Ponte Vecchio, which stacks vertically and bridges laterally at once.