Out-of-Order Superscalar Execution: Tomasulo's Algorithm, Register Renaming, Reorder Buffers, Load-Store Queues, Memory Disambiguation, and Pipeline Flushes

Deep End Era. Engineering with Sankalp · Oct 29, 2026 · 1h

If a four-gigahertz processor waited patiently in line every time a memory load missed in the Level-One and Level-Two caches, it would spend eighty percent of its life frozen solid. Instead, every modern high-performance CPU is a hardware dataflow engine in disguise. We trace out-of-order superscalar execution from Robert Tomasulo's 1967 IBM 360/91 and the MIPS R10000 to Register Alias Tables, Reorder Buffers, wakeup-select matrices, and Load-Store Queues.

Chapters

00:00:00 Opening: The Four-Hundred-Cycle Chasm

00:04:29 Why In-Order Pipelines Stall: The Three Data Hazards

00:08:49 Nineteen…