Nope. ReadyBoost takes advantage of external flash-based memory
by using it as cache due to its seek time. It's like VM on flash
instead of HDD. So if you pluck a HDD for ReadyBoost, it's as good
as allocating more VM in the primary HDD.
Using ReadyBoost-capable flash memory (NAND memory devices) for
caching allows Windows Vista to service random disk reads with
performance that is typically 80-100 times faster than random reads
from traditional hard drives. This caching is applied to all disk
content, not just the page file or system DLLs. Flash devices are
typically slower than the hard drive for sequential I/O, so to
maximize performance, ReadyBoost includes logic to recognize large,
sequential read requests and then allows these requests to be
serviced by the hard drive.
- Wikipedia
