Computer Operation Times in Human Scale.

It's important to know the time scale of computers.In my experience programmers use random times for sleep, pause or retry - oh lets pause for a 1 second!! - thats small for us humans, thats a lot of time in Computer's time scale. 

Following table gives a sense of mapping from computer time scale to human time scale.

The table is from Peter Norvig's site (very popular): http://norvig.com/21-days.html#answers

The mapping is from Erik Meijer - Director of Engineering Facebook.

Operation	Timing in Computer Time Scale	Timing in Human Time Scale
execute typical instruction	1/1,000,000,000 sec = 1 nanosec	1 second
fetch from L1 cache memory	0.5 nanosec	0.5 seconds
branch misprediction	5 nanosec	5 seconds
fetch from L2 cache memory	7 nanosec	7 seconds
Mutex lock/unlock	25 nanosec	0.5 minutes
fetch from main memory	100 nanosec	1.5 minutes
send 2K bytes over 1Gbps network	20,000 nanosec	5.5 hours
read 1MB sequentially from memory	250,000 nanosec	3 days
fetch from new disk location (seek)	8,000,000 nanosec	13 weeks
read 1MB sequentially from disk	20,000,000 nanosec	6.5 months
send packet US to Europe and back	150 milliseconds = 150,000,000 nanosec	5 year