Editing IBM PALM processor (section)

=== GETA Priority Encoder (8-Way Hardware Dispatch) ===

The '''GETA''' instruction (opcode `0xyF`) is one of PALM's most distinctive hardware features. GETA performs an 8-way priority decode of the 8 bits on Bus In, mapping the position of the leftmost zero into an addend of 0, 2, 4, 6, 8, A, C, or E (always even), which is then added to the destination register.

When the destination register is '''R0''' (the IAR), GETA becomes an '''8-way computed dispatch in a single instruction''' — the canonical "jump table in hardware" mechanism used throughout the executable ROS to dispatch I/O interrupts and emulated S/360 opcode classes. Without GETA the same dispatch would require a longer skip-chain.