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* term: 40-column text terminal on the CGB LCD (4x8 dynamic tiles)user5 days1-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add a background-tile text terminal that packs TWO 4px-wide characters into each 8x8 tile, giving a 40x18 grid instead of the 20x18 you'd get from an 8x8 font. The tilemap is static (one dedicated VRAM tile per screen position); we rebuild a tile's 16 bytes from two glyphs whenever a character changes. 360 tiles exceed the 256 a single tilemap can address, so positions 256-359 live in VRAM bank 1 via the CGB tilemap attribute bank-bit -- hence CGB-only. - Switch the ROM to CGB (rgbfix -C). Safe for the FS: every process has PROC_WRAMB=1, so SVBK stays on bank 1 and the WRAMX FS caches don't move. - CGB BG palette 0 = white bg / black text via BCPS/BCPD. - src/term.asm: term_init (palette + static tilemap + clear buffer), build_tile (combine two 4px glyphs -> one 8x8 tile, correct VRAM bank), term_redraw (rebuild all tiles), term_puts, term_show, term_test. - src/font.asm: 96-glyph 3x5-in-4x8 font, generated by tools/genfont.py. - 40x18 text buffer at $D600 (WRAMX, above the FS caches). - tools/ppmview.py: render a --shot PPM as ASCII so the LCD is inspectable from the shell during development. Verified via emulator screenshot: "GBOS TERMINAL", the alphabet, and a bank-1 row all render legibly at 40 columns. Serial shell + filesystem still work unchanged. Note: a full term_redraw builds 360 tiles and takes ~8 frames; fine for incremental single-char updates, but scrolling needs a smarter path (next milestone). Input (no keyboard) is also still TODO.
* fs rewrite stage 2: inodes + root directory (block-based, persistent)user6 days1-2/+1
| | | | | | | | | | | | | | | | - fs.asm: a real block filesystem on the persistent block device - superblock, block/inode bitmaps, a 32-entry inode table (type, size, 8 direct block pointers -> files up to 2 KiB), and a root directory of 16-byte entries. Metadata cached in WRAMX; one-block data cache streams file/dir blocks. - same syscall interface (open/getb/putb/list/remove) -> tools unchanged; ls now enumerates until flist() runs out (16 files, was hardcoded 8). - old 8-slot WRAM FS removed; cart RAM partitioned: process banks 0-7, disk 8-11. - two register-clobber bugs fixed: alloc_block/alloc_inode returned the bitmap-block number (write_bitmap clobbers C); db_use loaded the wrong block on a transition (db_flush->write_block clobbers C) -> multi-block files broke. - verified: 10+ files, multi-block (300-byte) files, delete, and persistence across reboots. Debug 'blk' disk tool retained (fill/peek). - README: document the block filesystem.
* fs rewrite stage 1: persistent block device (bounce buffer, cart SRAM)user6 days1-1/+8
| | | | | | | | | | | | | | - blk.asm: read_block/write_block move 256-byte blocks between battery-backed cart-RAM banks (8-11, the 'disk') and a WRAM bounce buffer. Banking is hidden in those two routines; they inline the 'restore my bank' step so they never touch the stack while the disk bank is mapped over the process's $A000 window (the stack lives there too -- a call/ret would rug-pull it). - format-on-first-boot: superblock magic in block 0; otherwise the disk persists. - cart RAM bumped to 128 KiB (-r 4); process banks 0-7, disk banks 8-11. - debug tool 'blk fill/peek' + syscalls to validate round-trip and persistence. - verified: round-trip incl. cross-bank (block 100 -> bank 11); block survives a reboot via .sav; magic intact (no reformat on 2nd boot). - old WRAM 8-slot FS still backs the tools until stages 2-3.
* filesystem: a RAM FS (WRAMX) + ls/cat/save/rm; wc/head read filesuser6 days1-0/+1
| | | | | | | | | | | - fs.asm: 8-slot RAM filesystem in WRAMX ($D000-$DFFF), name[8]+len[2]+data[502]; syscalls open/close/getb/putb/list/remove, seeded with a 'readme' at boot. - libc: open/close/fgetc/fputc/flist/fremove wrappers + O_READ/O_WRITE/NOFD. - tools: ls, save (stdin->file, one line), rm; cat/wc/head now take a file arg. - fix: syscall dispatch clobbers A, so putb takes its byte in E (was reading the handler's low address byte, 0xDC); ls NUL-terminates 8-char names. - verified: save/cat/ls/rm cycle; wc readme -> '2 7 38'; head -n 1 readme. - README: document the filesystem + the A-clobber ABI note.
* kernel: implement fork()user6 days1-9/+3
| | | | | | | | | | - sys_fork: switch to a kernel stack, bump-allocate a cart-RAM bank, copy the parent's 8 KiB bank via a WRAM bounce buffer, plant a switch-in frame so the child returns 0 to the post-fork PC, fill the child PCB (shared ROM text) - add AllocRamBank (bump allocator) + FindFreeSlot helpers - demo: init forks; parent prints P, child prints C (PCPC...); nested fork gives three distinct pids (123...) - README: document the fork mechanism, mark syscall status
* gbos scaffold: working cooperative microkernel (verified ABAB in emulator)user6 days1-0/+90
- fix ClearKernelRAM clobbering the kernel stack (only clear $C000-$CBFF) - fix SyscallTrap clobbering DE (buffer arg) during table dispatch - README: run via ~/dev/gbc --headless; note bring-up bugs