How To Reduce server mysql load on Multisite Networks?

Hello,

We’re running a dedicated server with 7 different WordPress networks, with approximately 20-40 sites per network. The websites are primarily informative, involving a low amount of images. Nothing too crazy going on with them.

Our server specs are as follows:

– Intel Core i3-3220 3.30 Ghz

– 2 drives 1000GB each

– 12,000GB bandwidth

mysql is running around 300-400% CPU and is making the server unstable – causing it to crash randomly.

We aren’t currently using any cache plugins, maybe that would help?

Do you have any suggestions on reducing the load of mysql?