ReadyBoost FAQFrom Matt Ayers:
I'm the Program Manager in the Microsoft Windows Client Performance group and own the ReadyBoost feature. I wanted to give some offical answers based on the excellent questions and discussions that I've seen in this blog, to date. Also, I'll be using this as a starting point for the official ReadyBoost FAQ.
At 4GB currently. I thought it would be fun to use...I don't think it'll make much of a difference on a machine with 2GB of RAM or more. I've heard reports that it definitely helps on machines with 512MB though.
My Tablet PC currently has 1GB installed. I'm getting a high-speed SD card for my camera, and I was planning to try that out as a ReadyBoost drive as well. I'm not sure when it'll be here though...it seems to be on back-order right now.
And he goes onto say:
Which supports what NR pointed out.Overall, as many posters have pointed out, the feature is designed to improve small random I/O for people who lack the expansion slots, money, and or technical expertise to add additional RAM. As y’all know, adding RAM is still the best way to relieve memory pressure.
Q: Ok... 256M-4GB is a pretty big range... any recommendations?
A: Yes. We recommend a 1:1 ratio of flash to system memory at the low end and as high as 2.5:1 flash to system memory. Higher than that and you won't see much benefit.
you must make sure the flash drive is "ready-boost" compatible otherwise it won't work - or at least make no difference because of the slow write speed.