Registers in common between a2xx and a3xx
Address mode for a5xx+
Line mode for a5xx+
Note that Bresenham lines are only supported with MSAA disabled.
Blob (v615) seem to only use SAM and I wasn't able to coerce
it to produce any other command.
Probably valid for a4xx+ but not enabled or tested on anything
but a6xx.
Produces garbage
Causes reads from an invalid address
Results in color being zero