Apple's M5 Pro and M5 Max processors employ vertically-stacked dies using the UltraFusion architecture previously seen in the company's Ultra chips. This design approach allows multiple chip dies to be stacked on top of each other, reducing physical footprint while enabling extremely fast communication between components. The technique borrows from Apple's M2 Ultra and M3 Ultra designs.

Speaking with *Heise Online*, Apple's Anand Shimpi explained that the new M5 chips split functions across two different dies that aren't mirror images of each other. Unlike traditional 3D packaging that stacks identical chiplets, Apple's approach gives engineers more control over thermal management by avoiding alignment of heat-producing sections. This architectural choice reportedly helps the M5 Max run cooler than its M4 predecessor under heavy loads.

The stacked die design also provides Apple with manufacturing flexibility. The company can combine different chiplets for various chip variants, potentially adding different GPU configurations while keeping CPU elements consistent. This modular approach allows Apple to create multiple chip versions more efficiently than designing separate single-wafer chips for each configuration, potentially reducing production costs and complexity.