Machine Characteristics - Timers

This is one of a number of machine-characteristics.

Timers

The cells in this table each show the values for PC timers 0, 1 and 2 in order. Any unusual settings are marked with a ** symbol.

Machine	Timer	Read/write modes	Counting modes	Binary or BCD
Dell Latitude XP 475D laptop. 80486 75MHz. Phoenix BIOS 1.10	0 1 2	11 (both) 01 (msb) 11 (both)	mode 3 mode 2 mode 3	binary binary binary
AOpen motherboard. Pentium 3 600MHz. Award BIOS 3.60	0 1 2	11 (both) 01 (msb) 11 (both)	mode 3 mode 2 mode 3	binary binary binary
Viglen MPC-L. Geode 399MHz. ION A503 BIOS	0 1 2	11 (both) 01 (msb) 11 (both)	mode 3 mode 3 ** mode 3	binary binary binary
Asus EEE 4G netbook. Celeron M ULV 630MHz. AMI ASUS 701 BIOS	0 1 2	11 (both) 01 (msb) 11 (both)	mode 2 ** mode 2 mode 3	binary binary binary
Gateway laptop. Dual-core Core 2 T5300 1.7GHz. Phoenix BIOS	0 1 2	11 (both) 01 (msb) 11 (both)	mode 3 mode 2 mode 3	binary binary binary
Jetway NC91. Dual-core Atom 1.6GHz. Phoenix-AwardBIOS	0 1 2	11 (both) 01 (msb) 11 (both)	mode 3 mode 2 mode 3	binary binary binary

Note that AMI tend to use mode 2 (rate generator) for counter 0 rather than the more-widely used mode 3 (square wave). This doesn't affect the frequency at which interrupts are generated but mode 2 does make it easier to use as a pollable timer.