ReadyBoost - Using Your USB Key to Speed Up Windows Vista

One very cool feature of Windows Vista – especially for machines not natively equipped with the kind of horsepower to fully enjoy the rich visuals of Windows Presentation Foundation (Avalon) applications is ReadyBoost. ReadyBoost enables you to plug a USB key into your machine and have Windows Vista use it as memory. I hadn’t actually used this myself, but had heard of it long ago. When a reader emailed me asking if this was an urban legend, I decided to check it out for myself and was very impressed with how easy and seamless the process is.

Installing/Configuring the USB Key as Memory

First I took a standard USB 2.0 key (I’ll list the prerequisites shortly) and plugged it into my machine. I’m running Windows Vista Beta 2, Build 5346, but I’m told that this works with the latest CTP made available to beta and TAP members as well as MSDN Subscribers. Upon plugging the USB key into my computer, I was greeted with the standard "AutoPlay" dialog box asking how I wanted to the operating system to treat the USB key. However, with ReadyBoost I get the additional option (circled below in the screen capture) of using the key to "speed up my system".

AutoPlay dialog box displayed when a valid USB Key is inserted into a machine running Windows Vista

Once I click the "Speed up my system" option, the Properties dialog box for the device is displayed where I can specify to start/stop ReadyBoost usage of the device and how much space I want used as a memory cache. (Actually, according to one of the Product Specialists here, this space is used more as a flash-based page file than true RAM, but the impact is that the more space you choose here, the more benefit you’ll get in terms of overall system performance.)

The device Properties dialog box allows you to turn on/off ReadyBoost for that device and to set the exact size of the cache.

(In order to return to this dialog box, open the Computer window, right-click the drive (F: in this case) and select Properties. From there, click the Memory tab (as shown in the previous screen capture and adjust the settings as needed).

For the inquisitive, opening the drive in an Explorer window reveals that ReadyBoost has created a cache file of the specified size.

Example cache file created by ReadyBoost on a USB Key

Things to Know About ReadyBoost

If you have a USB key configured to use ReadyBoost and then insert a second key, Windows Vista will display the Properties dialog box where you’ll see the message on the Memory tab as shown in the following screen capture.

Example of a USB Key that cannot be used by ReadyBoost as it doesn’t have enough free space for a cache

While ReadyBoost will work with other devices – such as SD Card, CompactFlash, etc. – I’ve only used it with a USB key and here are the baseline requirements the team gave me regarding what ReadyBoost will work with:

  • The USB Key must be at least USB 2.0
  • The device must be able to do 3.5 MB/s for 4 KB random reads uniformly across the entire device and 2.5 MB/s for 512 KB random writes uniformly across the device.
  • The USB Key has to have at least 64mb of free space


Update: Due to so many questions about this feature, I've tracked down the Program Manager (owner) of this feature - Matt Ayers. Matt has put together a complete ReadyBoost FAQ for everyone that I've posted in a separate blog entry.
Therefore, feel free to make comments here, but if you have any questions, first check out the FAQ and if it's not answered there, post me a question and I'll see if Matt can update the FAQ with your question/answer.