[TechnicallyComputers]

The overlay's single "60 FPS" was the VI rate (one tick per run_frame), so a 30 fps N64 game read 60. It is now three labelled rows:

FPS    30.0     the game's own pictures a second
VI     59.9     frames the core finished and presented a second
ms/VI  5.10     the runner's measured run_frame time per frame (headroom vs 16.7)

Changes

• rcore rev 8: rcore_frame appends game_frame (0 = the core cannot tell). Read only when struct_size covers it.
• Link 2.2: FrameDone appends game_frame and work_ns. It is the first message to grow. A 2.2 runner sends the 2.1 size (24 bytes) to a 2.1 hub, and a 2.2 hub reads a 2.1 runner's message with both fields 0. CoreLink::frame_stats() keeps the running totals.
• Overlay: Osd::note_counters(now, {frames, game, work_ns}).
  • Each rate covers the last second. FPS is anchored on the samples where the game's count moved, so it doesn't jitter by ±1.
  • Digits refresh 4×/s. Labels are dim and values white. A reading the core or link can't supply shows --.
  • note_frame() still works for a host with no counters (VI only).
• Docs: CORE_ABI.md (rev 8), CORE_LINK.md (2.2), OVERLAY.md.

Checked

• ctest: 30/30. That includes overlay (counters, uneven arrival, turbo, reset, pause, label colours, and FPS within 29.9–30.05 for a 29.97 game) and the new link_frame_stats test (fake core, game 5 of 10, work measured).
• n64lle core with this runner on Pokemon Stadium (fixture package, 600 grants) gives frame stats: game 522 work measured. 522 matches the VI model's own VI_RATE swaps=522 ("a new buffer every 2 fields = 29.91 fps").
• retro-overlay-test --dump renders the readout and was inspected. It was not captured on a live hub window: the window was behind other windows and there is no Xvfb here, so the on-screen check is still owed.

Not tested

• The 2.1 interop path in both directions. The size logic is what's described above; no 2.1 peer was run against it.

Companion PRs: n64lle (fills game_frame) and Retro-Launcher (the hub feeds note_counters; bumps this submodule).

Release note: n64lle's fetch_release.py requires the runner's draft revision to equal the core's, so Runtime and n64lle releases with rev 8 must be cut together.

🤖 Generated with Claude Code