Coriolis2 180nm layout

Simple floorplan

Register files

There are 5 register files: SPR, INT, CR, XER and FAST.

Access to each of the ports is managed via a "Priority Picker" - an unary-in but one-hot unary-out picker - which allows one and only one "user" of a given regfile port at any one time.

Computation Units

There are 8 Function Units: ALU, Logical, Condition, Branch, ShiftRot, LDST, Trap, and SPRs.

Each Function Unit has operand inputs and operand outputs. Across all pipelines there are multiple Function Units that require "RA" (Register A Integer Register File). All of such "RA" read requests are (surprise) connected to the same "Priority Picker" mentioned above: likewise all Function Units requiring write to the "RT" register are connected to the exact same "RT-managing" Write Priority Picker.

Load Store Computation Unit(s)

Load/Store is a special type of Computation Unit that additionally has access to external memory. In the case where multiple LDSTCompUnits are added, L0CacheBuffer is responsible for "merging" these into single requests.

There are however two L0 Caches (both 128-bit wide), with a split on address bit 4 for selecting either the odd L0 Cache or the even L0 Cache.

Each of the two L0 caches has dual 64-bit Wishbone interfaces giving a total of four 64-bit Memory Bus requests that will be merged through an Arbiter down onto the same Memory Bus that the I-Cache is also connected to.


Instructions are decoded by PowerDecoder2, after being read by the simple core FSM from the Instruction Cache. Currently this is an extremely simple memory block, to be replaced by a proper I-Cache with a proper connection to the Memory Bus (wishbone).