What is Readyboost?

Readyboost is NOT virtual RAM from a flash drive.
Readyboost is NOT RAM at all.

Readyboost is a cache used by your hard drive. Basically it copies stuff you normally use to the speedy Readyboost cache, where it can be used faster. Readyboost give an all round performance boost, and is more noticeable with older, slower hard drives. The more you have, and the faster it is means more boost.
Readyboost yields the most with small file browsing, boot up time, windows operations, and some programs you use.

Just wanted to clarify some things.

I have 20GB of readyboost, I got that instead of upgrading my HDD to a SSD or hybrid.

There have been many tests done online that show Readyboost's advantage is really only present with systems running 1 GB or less of system memory. Once you go over 1 GB, especially in today's systems with 4 GB and up, Readyboost doesn't really serve a purpose. It was meant as a place to store your carryover cache (when you don't have enough physical memory) that provided quicker access times than your HDD. Caching is minimal when enough system memory is present, negating anything ReadyBoost would do. It's pretty much been relegated to a past technology...not something used currently.

DeaconFrost said:

There have been many tests done online that show Readyboost's advantage is really only present with systems running 1 GB or less of system memory. Once you go over 1 GB, especially in today's systems with 4 GB and up, Readyboost doesn't really serve a purpose. It was meant as a place to store your carryover cache (when you don't have enough physical memory) that provided quicker access times than your HDD. Caching is minimal when enough system memory is present, negating anything ReadyBoost would do. It's pretty much been relegated to a past technology...not something used currently.

I'd say that 20GB of readyboost on my system, with 8GB of RAM, does help, I can noticeably see it.
Correction my friend, Readyboost becomes useful if your using around double the amount of your RAM, according to Microsoft. Folks with SSDs don't need Readyboost though.

You aren't the first person to come in here and make that declaration, but the truth is, it doesn't make a difference anymore. It's been tested and beaten to death, several times over on performance forums, such as [H]ardForum.

HTG Explains: Is ReadyBoost Worth Using? - How-To Geek

http://helpdeskgeek.com/windows-7/wh...t-worth-using/