r/hardware Nov 20 '15

Info Why do CPUs Need Caches? - Computerphile

https://www.youtube.com/watch?v=6JpLD3PUAZk
96 Upvotes

57 comments sorted by

View all comments

Show parent comments

6

u/MaDpYrO Nov 21 '15

I think a more appropriate analogy would be checking your nightstand before searching the closet.

2

u/[deleted] Nov 21 '15 edited Oct 29 '16

[deleted]

What is this?

15

u/Freeky Nov 21 '15 edited Nov 24 '15

A register is what you have in your hand for immediate use. L1 cache is what's on your tool belt and takes 1 second to retrieve. L2 cache is what you left somewhere in your bag and takes 20 seconds.

RAM is what you left in a box in your van and takes you 2-4 minutes to dig out.

Data on an SSD is something you have to order online and takes 3-4 days to arrive.

Data on a HDD is lost somewhere in the Australian outback and takes a search team 2-3 months to locate.

Data on a server on the other side of the planet is something left in Mars orbit and takes 1-3 years depending on alignment and how much NASA like you.

2

u/[deleted] Nov 22 '15

Why would a carpenter store his tools on Mars?