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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.
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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.
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The kernel had no clock: TimerISR was a reti stub, IEF_TIMER masked, and
IME was never enabled - the vectors were decorative. sys_sleep just polls
DIV deltas per-process; nothing counted globally.
Now: TAC runs the hardware timer at 16384 Hz with TMA=0, so TIMA overflows
at exactly 64 Hz; TimerISR increments a monotonic 32-bit wTicks (wraps
after ~2.1 years). Scheduling stays cooperative - the ISR is transparent.
Enabling IME in a kernel written for zero interrupts needs care wherever
SP points into memory whose bank is being switched (an IRQ pushes onto SP):
- read_block/write_block map the disk bank over the $A000 window that
holds the caller's stack -> di/ei around the transfer (~2ms, well under
the 15.6ms tick period, so no tick is ever lost)
- hSwitchTo switches SVBK + cart-RAM banks under the outgoing stack ->
di on entry, ei once the incoming stack is mapped
- fork already runs on KSTACK_TOP2 (fixed WRAM) - safe as-is
- term_putc's SVBK switch only remaps $Dxxx, stacks live in $Axxx/$Cxxx
SYS_UPTIME (36) copies the counter (4B LE, di/ei so the read can't tear)
to a user buffer; libc gticks(); usr/uptime.c formats 'up [Nd] H:MM:SS'.
uptime avoids SDCC long div/shift entirely: sm83.lib modules link into
their own areas that land in the $A000 RAM window (latent build.sh trap,
documented there) - bytewise >>6 plus bounded subtraction loops instead.
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Programs that own their main loop (the IRC client) need to poll for
typed input without blocking. pollin() only sees the on-screen keyboard;
bytes injected over the link (gbhub 'type', for scripted/hub-driven
sessions) land in the kernel console ring, previously only drained by the
blocking KGetc path. Add SYS_POLLCON: a non-blocking con_pop for
userland.
Also enlarge that console ring 16 -> 64. One net_pump drains an entire
serial burst into the ring at once, so a whole injected command line has
to fit or bytes are dropped and lines merge (a 20-char command came out
truncated and glued to the next). 64 covers a full line; mask stays a
power of two.
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A Game Boy sitting at the shell prompt now services the network instead of
being deaf until you run netd: KGetc (the console input wait) pumps net_pump
each poll, so inbound pings are auto-answered while idle. net_pump gained an
in-frame model and routes any non-framed link bytes to a small console-input
ring (con_push/con_pop), so a headless-injected command still reaches the shell
while SLIP frames go to the stack. Removes the old SLIP-skip-in-KGetc hack.
Verified: two Game Boys on the hub, GB0 idle at the prompt (no netd), GB1
`ping 10.0.0.2` -> 4/4 replies, routed GB1->hub->GB0->hub->GB1.
(Separate, pre-existing: gbhub *spawn* mode and windowed gbjoin can drop an idle
link socket - under investigation; daemon mode + headless is solid.)
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There was no time source at all (IRQ vectors just reti; scheduler is purely
cooperative). The DIV register (FF04) free-runs at 16384 Hz regardless of
interrupts, so sys_sleep accumulates DIV deltas across SchedYields (other procs
keep running) until the requested number of 1/64-second units elapse.
- SYS_SLEEP(34): B = 1/64s units; libc gsleep(units) / msleep(ms) wrappers.
- ping now msleep(800) between echoes, so it paces like real ping instead of
blasting all four at once.
Verified real-time (capped emulator): replies land ~0.85s apart. In --uncapped
runs the delay is GB-time (fast wall-clock), as expected.
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The link port is both the console-input fallback and the network. At the shell
prompt the host's multicast (mDNS/LLMNR/IGMP) was fed to the serial and KGetc
read those packet bytes as console input -> garbage in the shell, OSK unusable.
Two-part fix:
- KGetc now skips SLIP frames (0xC0-delimited) on the serial console path, so
inbound packets never surface as console input. Plain injected bytes (the
headless tunbridge command path) still pass through. New wConInSkip flag.
- netboot/tunbridge only forward IP packets destined to 10.0.0.2 (drop the
multicast noise at the bridge).
Verified: GB sits at a clean "/#" prompt while all packets (noise included) are
forwarded; being-pinged (3/3) and wget still work. On the emulator, the OSK is
SELECT=space, START=enter, A=z, B=x, d-pad=WASD/arrows.
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The network stack moves into the kernel. src/socket.asm owns SLIP framing,
IPv4, RFC1071 checksums, and ICMP; programs now speak a socket API through one
syscall (SYS_NET, DE=&netreq dispatched by op): net_socket/connect/send/recv/
close/poll (c/sock.h). No program touches SLIP, IP headers, or checksums.
- Socket table (4 sockets) + tx/rx buffers in WRAM0; our IP = 10.0.0.2.
- net_pump: drains the link, reassembles SLIP frames, demuxes IPv4. Inbound
ICMP echo requests are auto-answered in-kernel, so the GB replies to pings
whenever any process pumps RX.
- ICMP sockets: send() emits an echo request to the connected peer; recv()
returns the matching reply (with a spin/yield timeout).
ping.c is now a ~15-line socket client; netd.c is just `for(;;){net_poll();
yield();}`. Verified over tunbridge:
/# ping 1.1.1.1 -> replies from the real internet (kernel builds it all)
host# ping 10.0.0.2 -> 4/4, 0% loss (kernel auto-answers)
Gotchas recorded: gbos.inc isn't a make dep (touch asm after editing); this
crt0 doesn't copy initializers (fill arrays at runtime); and the arg string at
0xA000 overlaps _DATA, so parse targets must sit past it (big buffer first).
UDP and TCP sockets build on this same core next.
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The application layer of the link-port demo, and it ties the whole system
together: the LCD terminal displays, the on-screen keyboard types, and the
link port carries a live chat.
Kernel: sys_srecv_nb (non-blocking link receive; A=byte, CF=none) and
sys_pollin (poll the OSK for a typed char without blocking) - syscalls
31/32. Both are what a poll loop needs to receive and type at once.
Userland: c/chat.c runs a poll loop - it feeds non-blocking bytes through a
SLIP receive state machine and prints whole incoming frames as messages,
while pollin() drives the on-screen keyboard; SELECT shows the keys, type a
line, START sends it as a frame. libc srecv_nb()/pollin().
Host: tools/gateway.py --mode chat is a simple bot peer (echoes each GB
message and injects a few async ones); --keys can drive the OSK for tests.
Verified: the gateway pushes 'welcome', '<alice> hey gameboy!', '<bob> nice
link cable' unprompted and the GB displays all three (async receive); typing
'hi' on the OSK echoes it and emits the SLIP frame \xC0hi\xC0 (send). A Game
Boy in the chat, keyboard on screen, over the link cable.
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First step of link-port networking. The LCD terminal + OSK freed the serial
port from console duty, so it can be the network link.
Kernel (src/net.asm): raw link-port serial that bypasses the console/
terminal - sys_ssend (transmit, GB drives the clock) and sys_srecv (receive,
GB slave, blocks by yielding). Syscalls 29/30.
Userland: libc ssend()/srecv(); c/necho.c does SLIP (RFC 1055) framing over
them - send a packet, receive the reply, print it.
Host: tools/gateway.py wraps the emulator, owns its link serial, speaks SLIP,
and (for now) echoes every frame back - the "link cable adapter". Console
(ASCII) bytes on the same channel are printed for visibility.
Verified: `necho` sends a SLIP frame, the gateway decodes+echoes it, and gbos
prints the reply - a real framed round-trip over the Game Boy link port.
Next: swap the echo for actual network ops (DNS/HTTP or IRC/chat).
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Replace the shell's temp-file pipe hack with proper in-kernel FIFOs.
Kernel (src/pipe.asm, new):
- A small pool of bounded ring buffers (PIPE_MAX=2, 64 B each) with
writers/readers refcounts. Pipe fds are $F0+idx*2 (read) / +1 (write);
$FF stays "console".
- SYS_PIPE allocates one (writers=readers=1) and returns the read fd
(write = read+1). getb/putb/close dispatch pipe fds here; sys_exit drops
the refcounts held as PROC_STDIN/PROC_STDOUT.
- Blocking with SchedYield, which is the flow control: read blocks while
empty with a writer (EOF once writers hit 0), write blocks while full
with a reader, and if the last reader is gone the writer is killed
(SIGPIPE -> exit 141). Cooperative-scheduler friendly.
Shell (c/sh.c):
- run_pipeline(): split on '|', make a pipe between adjacent stages, and
fork ALL stages concurrently (no wait between), wiring stdin/stdout;
then wait for all. Per-stage >/< still honored; orphaned pipe ends are
closed on a lookup miss so EOF/EPIPE propagate.
- Drop the __pipe temp file and its 2 KB / serialized limits.
libc: pipe(). New c/ptest.c exercises the FIFO (write, read back, EOF).
Now works (old version couldn't): multi-stage a|b|c; streaming beyond 2 KB
(count 120 | wc = 3372 bytes through a 64 B buffer); early-exit SIGPIPE
(count 200 | true kills count instead of hanging/overflowing a file).
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A joypad-driven keyboard that costs zero permanent screen space: it lives
on the GB window layer, so SELECT just flips LCDC bit 5 (window enable) and
the terminal's background layer underneath is never disturbed.
- src/joypad.asm: read $FF00 with edge detection (wPadCur/Prev/New).
- src/osk.asm: 3x20 key grid (letters, digits, space, punctuation, plus
Enter/Backspace) built once into spare bank-1 VRAM tiles (104+) and laid
out on the $9C00 window map, docked to the bottom 3 rows. The highlighted
key is a palette swap on its window attribute byte (CGB BG palette 1 =
inverted), so moving the cursor is 1-2 attribute writes with no tile
rebuilding. SELECT toggles, d-pad moves, A types.
- KGetc's console poll loop now polls the joypad and osk_handle each
iteration; a key press returns its byte to the reader exactly like a
serial byte, so the shell is oblivious to the input source.
Verified in the emulator (via --keys): SELECT shows the keyboard, the
highlight tracks the d-pad, and typing "ls"+Enter runs the command and
lists the files; a second SELECT hides it and reclaims the full 18 rows.
Known limitation: the OSK overlays the bottom 3 terminal rows, so if the
prompt has scrolled to the very bottom the current input line can be
hidden. A follow-up can add a scroll region (terminal uses rows 0-14 while
the OSK is up). Input over serial still works unchanged.
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KPutc's console path now renders each byte on the LCD terminal via
term_putc in addition to the serial write. Serial is kept so scripted
tests still capture output (and for link-cable/debug), while the shell,
command output, and echoed input now appear on-screen in the 40-col font
with a live cursor and scrolling. Dropped the boot-time term_demo; the
terminal starts blank and fills from real console traffic.
term_putc now saves/forces/restores SVBK=1 so it always reads and writes
the terminal buffer/state in WRAM bank 1, regardless of which process
context KPutc is invoked from (defensive; all procs currently use bank 1).
The stack lives in non-banked WRAM, so saving SVBK across the switch is safe.
Verified: a headless run of `uname; ls; echo hello world` renders each
prompt, the echoed command, and its output on the LCD (captured via the
new `--headless --shot` path), and serial capture is unchanged.
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- directories generalized: dir_find/dir_add/dir_remove take any dir inode;
every dir carries '.'/'..'. Path resolution (resolve / resolve_parent) walks
absolute or cwd-relative paths; open/mkdir/chdir/remove/opendir take paths.
- per-process cwd: PROC_CWD in the PCB (root by default, inherited on fork);
sys_chdir sets it, sys_opendir points ls at any directory.
- shell: 'cd' builtin + cwd-aware prompt; 'mkdir'/'ls <dir>' tools; 'exit'/'quit'
and EOF call poweroff() (clean shutdown via the $ED opcode -> reliable save).
- three HL/buffer-clobber bugs fixed along the way: resolve didn't preserve the
path cursor across dir_find; cur_cwd clobbered HL; resolve_parent set the final
name before resolve() overwrote wFsNameBuf (now copied after).
- verified: nested mkdir/cd/save, multi-level paths (cat docs/sub/b), and the
whole tree persists across a reboot.
- README: document directories + the poweroff opcode.
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- 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.
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- sys_reap: nohang reap of a finished zombie child (-> pid or 0).
- shell: 'cmd &' launches in the background (prints [pid], no wait); reaps
finished jobs at the prompt ([pid done]). Foreground now waits for its own
child specifically (loops wait(), reporting bg completions meanwhile) so kill
reports the right pid.
- spin: a process that yields forever - a target for ps/kill.
- verified: spin &; ps shows it; kill <pid> removes just that one; immortal
init; self-finishing bg worker reaped with [pid done].
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- PCB gains PROC_PROG (running program id), set by exec, inherited on fork.
- sys_kill(pid): reject pid 1 (immortal) and unknown/dead pids; mark the target
zombie, reparent its children to init, wake its parent if blocked in wait;
schedule away if a process kills itself. Reuses FindPcbByPid/ReparentToInit.
- sys_ps(slot,buf)->{pid,state,prog}; sys_progname(id) via NameTable reverse
lookup. NameTable gains sh/ps/kill.
- libc: kill/psget/progname; tools ps (pid state cmd) and kill <pid>.
- verified: ps lists sh(B)+ps(R); kill 1 refused; kill 42 fails.
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- kernel I/O routing: PCB gains PROC_STDIN/PROC_STDOUT (default console $FF),
inherited across fork. KGetc/KPutc route read/write/putc to the console or a
file fd. New syscalls: putc(16), setin(17), setout(18), lookup(19).
read/write now go through the routing; putc/puts/nl use SYS_PUTC.
- sys_lookup + NameTable move command-name resolution into the kernel.
- shell rewritten in C (c/sh.c): tokenizes a line, parses > / < / |, and drives
fork+setin/setout+exec+wait. Pipes run as 'a > __pipe ; b < __pipe' (temp
file). asm shell + cmdtab removed; StrEqual/SkipName kept for sys_lookup.
- libc: fork/exec/wait/setin/setout/lookup wrappers.
- verified: echo>file, cat file, wc<file, cat readme|wc -l, echo ...|wc.
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- fs.asm: 8-slot RAM filesystem in WRAMX ($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.
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- sys_read (SYS_READ): blocking console input via external-clock serial poll;
yields while waiting. Verified working (direct-echo cat: 'hi' -> 'hi').
- shell (PROG_SH): prompt/read/parse/fork+exec+wait; worker+hello programs;
StrEqual/SkipName helpers; command table.
- init now execs the shell.
- KNOWN BUG: storing the typed char to the line buffer at $A000 (cart RAM of an
exec'd program) corrupts the following sys_read; sys_write reading $A000 also
returns $3E. Kernel syscalls themselves are correct; isolating the cart-RAM /
exec RAM-bank interaction next.
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- exit(): zombie + status, reparent orphans to init, wake blocked parent,
schedule away forever (resources reclaimed by the reaper)
- wait(): scan for a zombie child; reap (free cart-RAM bank + PCB slot) and
return pid/code; block PS_BLOCKED + yield if children still live; $FF if none
- cart-RAM banks are now a free list (wBankUsed bitmap): AllocRamBank/FreeRamBank
- scheduler: FindNextReady returns carry when nothing runnable; yield idles
instead of blindly picking slot 0
- helpers: FindPcbByPid, ReparentToInit
- demo: init forks 3 workers -> exec -> exit(pid) -> wait/reap => wwwR2R3R4!
verified bank recycling with 6 workers over 3 banks (w2w3w4w5w6w7)
- README: document the lifecycle + syscall status
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- sys_exec(B=program id): look up ProgramTable, point PROC_ROMB at the program's
ROM text bank, map it into $4000-$7FFF, reset stack, jp to entry (no return)
- programs.asm: two demo programs (ping/pong) ORG'd at the SAME $4000 in banks
2 and 3 - proves execution is driven purely by PROC_ROMB
- demo: init forks; parent execs PROG_PING (bank2, '1'), child execs PROG_PONG
(bank3, '2') -> '1212...', 2000/2000 balanced, zero garbage
- README: document exec + text-in-ROM model
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- 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
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