Brion Vibber on Nostr: The Atari 400/800 didn't have a real-time clock built in, so you couldn't query for ...
The Atari 400/800 didn't have a real-time clock built in, so you couldn't query for the actual time of day without add-on hardware.
But it did maintain a running count of vertical blank interrupts (a hair under 60 Hz), suitable for counting human-readable intervals and rates.
This 24-bit counter would roll over after about 3 days of continuous operation [calculation corrected] so it was *possible* it would roll over while you were using it...
https://www.atariarchives.org/mapping/memorymap.php#18,19,20
But it did maintain a running count of vertical blank interrupts (a hair under 60 Hz), suitable for counting human-readable intervals and rates.
This 24-bit counter would roll over after about 3 days of continuous operation [calculation corrected] so it was *possible* it would roll over while you were using it...
https://www.atariarchives.org/mapping/memorymap.php#18,19,20