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| author | user <user@clank> | 2026-07-18 10:10:04 +0200 |
|---|---|---|
| committer | user <user@clank> | 2026-07-18 10:10:17 +0200 |
| commit | 0cc9b0a8bdf774ee376937d5a6767ccdced51245 (patch) | |
| tree | 221326e7a86fa0121ae7eea1763a9f3ffa8100e6 /src/programs.asm | |
| parent | kernel: dmesg-style boot spew before init spawns (diff) | |
| download | gbos-0cc9b0a8bdf774ee376937d5a6767ccdced51245.tar.gz gbos-0cc9b0a8bdf774ee376937d5a6767ccdced51245.tar.xz gbos-0cc9b0a8bdf774ee376937d5a6767ccdced51245.zip | |
kernel: a real timer source (64 Hz tick IRQ) + uptime(1)
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.
Diffstat (limited to '')
| -rw-r--r-- | src/programs.asm | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/src/programs.asm b/src/programs.asm index 6dbc584..7c17fb5 100644 --- a/src/programs.asm +++ b/src/programs.asm @@ -133,6 +133,9 @@ ProgDhcp: SECTION "prog_irc", ROMX[$4000], BANK[32] ProgIrc: INCBIN "build/usr/irc.bin" +SECTION "prog_uptime", ROMX[$4000], BANK[33] +ProgUptime: + INCBIN "build/usr/uptime.bin" ; ----------------------------------------------------------------------------- ; PROG_SH (bank 3) - the shell, now written in C (usr/sh.c): parses >/</| and @@ -237,6 +240,8 @@ ProgramTable:: dw ProgDhcp db LOW(BANK(ProgIrc)), HIGH(BANK(ProgIrc)) dw ProgIrc + db LOW(BANK(ProgUptime)), HIGH(BANK(ProgUptime)) + dw ProgUptime ProgramTableEnd:: ; ----------------------------------------------------------------------------- @@ -306,4 +311,6 @@ NameTable:: db PROG_DHCP db "irc", 0 db PROG_IRC + db "uptime", 0 + db PROG_UPTIME db 0 |