apparently there is a glitch in the old version of half life where if you jump and move your mouse while strafing in that direction you will gain speed
you have to jump as soon as you hit the ground though
this allows you to move faster than running speed
so you go over 320 ups
i think ups means units per second and that means like inches per second
so its a cool trick
someone used it to beat half life in 20 minutes
and this is a 15 hour game
now this is only for old version. new versions have a speedlimit where if you go over 544 ups it will revert you to 320 ups
its a cool trick