gbos.git, branch master

demo: boot the SL0PBOY-forked BIOS in the README gif

2026-07-18T20:45:32Z

gbdemo resolves a bare --bios to bios/sl0pboy_bios.bin when present (else stock gbc_bios.bin). Generate the fork with the emulator's tools/mk_sl0pboy_bios.py. The gif now opens on the SL0PBOY boot animation - logo drop, colorize, chime - before gbos comes up.

term+libc: batched write rendering - one tile render per write(), 2.3x lines

2026-07-18T20:19:59Z

sys_write sets wBatch; render_cursor_tile - the single choke point all of term_putc's visible mutations pass through - then marks a dirty span (per LINE-SLOT, so spans survive scroll rotation for free) instead of rendering. term_write_end renders every dirty tile exactly once, then the cursor. Scrolls stay immediate (blank rebuild is cheap and artifact-free); file-bound writes flush for free. The enabler is in libc: puts() was a SYS_PUTC trap PER CHARACTER, so almost no console output ever went through sys_write. It now issues one SYS_WRITE for the whole string - one trap, one batch, and every line-printer (echo, irc, the shell) gets the batched path. Measured: 37-char write = 128k cycles (3.5k/char) vs ~8k/char down the per-char trap path. Full demo passes; GIF regenerated.

demo: boot through the CGB BIOS + double-speed ROM in the README gif

2026-07-18T20:11:07Z

spawn --bios shows the real power-on show (logo drop + splash) before gbos boots; gbdemo resolves a bare --bios to the emulator's bundled boot ROM by absolute path (the tmux pane cwd is wherever the user is). The screen-synced waitfor absorbs the extra ~4s - only the first prompt timeout got a bump. Regenerated with the double-speed kernel: same demo, boots and scrolls visibly snappier.

kernel: CGB double-speed mode - 2x everything (1.99x measured)

2026-07-18T20:06:35Z

KEY1 prepare + STOP at KernelInit (skipped on warm reboot if already fast). The PPU/LCD keep their normal rate; the timer and DIV double with the CPU, compensated at the two consumers: - TimerISR now fires at 128 Hz; a toggle byte keeps wTicks at 64 Hz (uptime semantics unchanged) - sys_sleep halves the DIV-delta accumulator's high byte (256 DIV ticks = 1/128 s in double speed) so gsleep/msleep stay real-time Measured: count 60 (scroll-heavy) 3.77s -> 1.89s wall; wTicks 64 Hz over 4s; ping's 800ms msleep pacing unchanged (2.77s for 4 echoes). sl0pboy already emulated KEY1/STOP + per-speed timer/PPU rates.

term: latch SCY in VBlank - fix ring-scroll shear on live displays

2026-07-18T19:56:21Z

The ring-scroll wrote SCY mid-frame; SCY is sampled per scanline (on hardware and in sl0pboy's PPU), so a scroll landing mid-frame rendered the top of the frame at the old offset and the bottom at the new one - a one-frame shear, invisible in frame-sampled GIF captures but ugly on a live sixel view. term_view_update now writes hSCY (HRAM) and a transparent VBlank ISR (push af / apply / pop af / reti, same profile as TimerISR) copies it to rSCY, so the view only ever moves at frame boundaries. The scroll's tile+map writes stay immediate: the new map row is invisible at the old SCY by construction (it's the ring row one past the visible 18).

term: SCY ring-scroll - scroll writes ONE map row; OSK toggle is 212 cycles

2026-07-18T19:50:22Z

The BG map's 32 rows become a ring: logical row L always lives at map row (wMapTop + L) & 31, and SCY = (wMapTop + wViewTop)*8 places the view. Scrolling bumps wMapTop, rebuilds the one new bottom line and writes its single map row (map_row_one); the other 17 rows move for free. The whole OSK view dance - shift the cursor above the keys, restore the backlog on hide - is now term_view_update: one SCY write, no map rewrite at all. OSK safety: the keyboard lives on the WINDOW layer, which SCY never moves. Stale ring rows can only appear under it: wViewTop = max(0, wCurRow-14) <= 3 is nonzero only while the OSK is visible, and the window covers exactly those bottom 3 rows (WX=7, WY=120). Verified: scroll + view shift + scroll-while-OSK-up + backlog restore all pixel-correct via VRAM screenshots; full README demo passes. term_scroll: 78.5k -> 35.6k T-cycles (857k pre-optimization: 24x). OSK toggle: 45k tilemap rewrite -> 212 cycles. Regenerated demo/gbos-demo.gif on the new renderer.

term: 3 more renderer wins - 10.9x scroll, 2.7x putc vs pre-cache

2026-07-18T19:42:27Z

1. color_setup memoization: a call with the same (colL,colR) pair as last time returns immediately (masks/attr still valid in WRAM). Runs of same-colored cells - i.e. almost all text - hit this. 2. build_tile blank fast path: two spaces = bg-only planes, 8 constant rows; term_scroll's cleared line and every blank region skip the glyph pipeline entirely. 3. build_tile two-phase rewrite: combine both glyphs into wRowBuf with pointers in registers (the old per-row 16-bit WRAM pointer walk was most of the blit), then compose planes unrolled with plane-0 masks in B/C. 4. term_write_tilemap attr pass: split each row at the pos-256 VRAM bank boundary into two tight cache->tilemap copy runs - no per-tile addressing or bank test. Measured (emulator cycle counter, ANSI test screen): term_scroll 857k -> 248k (attr cache) -> 78.5k T-cycles term_write_tilemap 723k -> 114k -> 45.4k term_putc 18.2k -> 6.7k A scroll is now ~1.1 frames of guest CPU (was 12); a full 40-char line prints in ~63ms of guest time (was ~173ms).

term: cache tile attrs in COL_BUF's spare stride bytes (3.5x scroll)

2026-07-18T19:32:16Z

term_write_tilemap's attribute pass ran color_setup - the full Fano palette walk - for all 360 tiles on every scroll. render_tile already computes the attr when a tile changes, so store it (COL_BUF + slot*64 + ACACHE + tcol; the stride's 24 spare bytes were free) and the attr pass becomes a table read. update_cursor_attr reads the cache too. term_init now redraws before writing the tilemap so the cache is warm. Measured entry-to-return with the emulator cycle counter, ANSI test screen content: term_write_tilemap 723k -> 114k T-cycles (6.3x), term_scroll 857k -> 248k (3.5x) - a scroll drops from ~12 frames of guest CPU to ~3.5.

docs: drop the link-drop investigation writeup

2026-07-18T19:02:47Z

hooks: clang-format pre-commit (changed lines only) + .clang-format

2026-07-18T18:57:37Z

Same setup as sl0pboy: git-clang-format scopes formatting to the lines each commit touches, re-adds the formatted files, and refuses partially-staged C files. Style file matches the house style (4-space, attached braces, 100 cols, short cases/ifs inline, no include sorting - order is load-bearing for SDCC userland). Enable once: git config core.hooksPath hooks