Unraveling Time: A Deep Dive into TTD Instruction Emulation Bugs

This report explains Microsoft Time Travel Debugging (TTD), its components (TTDRecord, TTDLoader, TTDRecordCPU, TTDReplay, etc.), and historical CPU emulation challenges (floating-point/SIMD, memory model, peripherals, self-modifying code, performance vs. accuracy). It documents an initial bug where running a heavily obfuscated 32-bit PE under TTD caused a crash that did not occur on real or virtual machines and notes that TTD trace files are useful for pinpointing such issues.