No it isn't.
ReadyBoost is not a replacement for RAM. ReadyBoost is basically a form of caching and will intercept reads and writes to your hard drive and then stores the data into the file located on the ReadyBoost device and since flash drives are faster than hard drives for random I/O operations, it will help the slow random I/O performance of hard drives. Have a read of the *ReadyBoost* section of this article here if you would like more of an in-depth understanding regarding ReadyBoost.
That article was quite the interesting read. Cheers for that
