gbos - a tiny Unix-flavored OS for the Game Boy Color (kernel, shell, coreutils in C, RAM filesystem) https://git.sl0p.foo/gbos.git/atom/sl0ppty.layout.kdl?h=master 2026-09-24T21:08:54Z 2026-09-24T21:08:54Z user user@clank 2026-09-24T21:08:54Z urn:sha1:be1a8f74e48d4ed2ae3a0b78a7137b4bc41a2969 An MBC5 cart has no RTC, so SNTP is the only route to a wall clock. ntpdate does one 48-byte UDP exchange on port 123 and hands the stamp to the kernel; SYS_SETTIME keeps it with the tick it arrived at, and SYS_GETTIME adds the elapsed ticks back, so date(1) is just formatting. /# ntpdate ntpdate: clock set from pool.ntp.org /# date Sep 24 21:01:23 UTC 2026 (host said 21:01:26) The clock does not survive a power cycle - which is exactly what /rc is for: `ntpdate` there and the machine boots knowing the time. All of it is bounded subtraction, no long division or shifts: SDCC pulls those from sm83.lib, whose modules link into the $A000 RAM window. The month tables are string literals for the same family of reason - an initialized array goes to _INITIALIZED at $A000 and the image overflows its bank ("buffer too small" out of makebin), which is how this first failed to link.