New always-on ring in the debug server: every vblank captures the display
area's raw 15-bit pixels AND the full 1024x512 VRAM as the ACTIVE RENDERER
sees it (GL: FBO truth via fbo_peek; SW: CPU truth), 64 frames of lookback.
Commands: display_ring_get (frame -> PNG), display_ring_aux (frame -> raw
u16 VRAM blob), display_ring_stats.
Purpose: FRAME-EXACT visual forensics. screenshot_file returns whatever is
on screen when the command lands (1-3 frames late), which cannot support
cross-renderer same-frame comparison; the ring can. Proven use (MMX6 sprite
triage): pulled the SAME deterministic frame from a GL run and a software
run, micro-cosimed the suspect sprite prim from the GP0 ring against the
same-frame captured texels/CLUT, and established GL and SW render the scene
pixel-identically with byte-identical texture content - reclassifying the
reported artifact from renderer bug to (pending Beetle oracle) game content.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Matthew Stanley
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