Sketch the chip's major parts, such as processors, memory and the roads between them, and decide how they work together.
Architects split the design into blocks (cores, accelerators, memories, interconnect, I/O), model performance, and choose clocking, power domains and the memory hierarchy. Software models test ideas before any hardware is written.
Performance modeling, microarchitecture trade-offs, interconnect and NoC topology, memory hierarchy and bandwidth, clock and power domain strategy, IP make-or-buy, partitioning with the floorplan in mind, and early power and area estimates.