Hardware Oddity Resource Aliasing

Halo 2 resource aliasing and tiled pitch

Evidence: Xbox observed through firsthand reverse engineering; assembly is original implementation evidence. Ryan Miceli reports roughly 25 render-target views backed by only four or five distinct buffers in Halo 2. His reconstruction includes ARGB and ABGR interpretations of depth storage. The published HD patch also uses D3D_CalcTilePitch when preparing modified targets; it does not merely substitute a larger logical width.

An address alone does not identify a captured texture. Use address range, format/channel interpretation, draw time, and most recent producer. Do not infer memory coverage solely from host-image dimensions when tiled pitch differs.

Proposed test: capture several widths around tile-pitch transitions and multiple formats over the same guest storage. Compare byte coverage, read-after-write ownership, and raw view contents before comparing the image.

Source: Miceli's Halo 2 HD investigation and patch discussion.

See also Memory & DMA and NV2A Graphics Architecture.