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Understanding ReadyBoost in Windows 7 - fixedByVonnie

Understanding ReadyBoost in Windows 7

ReadyBoost is a cheap, fast and in most cases, effective way to improve disk read performance for traditional hard drives.

ReadyBoost actually isn’t applicable to Solid State Drives because any speed gains with the SSD are already commensurate with the reading rates on a ReadyBoost drive.  You can read my article about how SSDs work, but the bottom line is that Windows automatically disables ReadyBoost on SSDs because it provide no palpable benefits.


Before we get started I need to promulgate a disclaimer: ReadyBoost is not like stepping in a sports car and pressing the accelerator to the floor.  You’re not going to notice a dramatic speed improvement in everything you do.  In other words, don’t expect an adrenaline rush from ReadyBoost because that isn’t going to happen.

The other thing to keep in mind is that ReadyBoost doesn’t provide a substantive speed enhancement on hard drives that spin at 7200 RPM or faster.  These drives already have high disk I/O so ReadyBoost isn’t really going to avail itself here.  This doesn’t mean you can’t benefit from ReadyBoost if you have a 7200 RPM hard drive, but it does mean that users with slower drives, such as 5400 RPM will notice a greater speed improvement.

How to find your Hard Drive RPM

You can Google your hard drive manufacturer to find the exact RPM value.  To find your hard drive vendor from within Windows, open the Device Manager by pressing the Windows Key + Pause Break or if you don’t have a Pause/Break key like me, click Start and enter this command:


Then in the device manager, expand Disk Drives and Google the name and add the keyword RPM.

Windows 7 Device Manager Hard Drive Model

So in my case I Googled this and found my RPM on the first hit.

ST9500420AS RPM

Ideal for Computers with a WEI less than 4.0

One other thing: ReadyBoost is ideal for systems that have a Windows Experience Index subscore less than 4.0.  To view your score, click Start, type cmd and press enter.  Then enter this command in the black window that appears:

View System Properties from Command Prompt

control system

Instantly the System Properties screen appears with your Windows Experience Index front and center.  I highlighted mine below.

Since I have a 5.9 WEI you can see I wouldn’t benefit much from ReadyBoost but it won’t hurt to enable it anway.

Windows Experience Index

Readyboost isn’t like free RAM

Finally, it’s important to be cognizant of the fact that ReadyBoost is not the same as more RAM.  ReadyBoost doesn’t give you more virtual RAM, it gives you more hard drive performance.  If you get any performance boost from a system running 2Gigs of RAM with ReadyBoost it’s because ReadyBoost made your hard drive more efficient, it really has nothing to do with RAM.

I needed to clear that up because a lot people get confused about that little caveat.

Which flash media can I use?

Most people enable ReadyBoost on USB flash drives; however, you can also use a SD card or even a CompactFlash card if needed.  Whatever kind you pick, just make sure it satisfies these two requirements:

  • At least 64KB of free space with a minimum total capacity of 256MB
  • A minimum of 2.5 MB/sec for reads and 1.75MB/sec for writes.

All modern flash drives satisfy the above criteria so you don’t need to worry.   These specs really only become an issue if you’re using a super antiquated flash drive. (something like an artifact from the early 90’s)

If you’re not sure about the specs, you can just plug the flash media in your computer and wait a few seconds for AutoPlay to appear with the ReadyBoost option.

Windows 7 ReadyBoost AutoPlay

How to make ReadyBoost work

You can either click Speed up my system in the Autoplay window or open My Computer (Windows Key + e for keyboard aficionados) and right click your flash media drive.

Next, pick Properties and select the ReadyBoost tab.

Enable ReadyBoost in Windows 7

I recommend clicking Dedicate this device to ReadyBoost for maximum performance.

ReadyBoost creates a disk cache file called ReadyBoost.sfcache in the top level (the root location) of your flash media.  All space is allocated at creation and fills with cached content as ReadyBoost uses the Windows SuperFetch algorithm to decide which files to send to the cache.  It’s important to note that all files in the ReadyBoost cache are encrypted using 128-bit AES so the cached content is relatively secure if you lose your drive or someone steals it.

How to make sure ReadyBoost is really working

You can use the Windows Performance Monitor tool and add ReadyBoost Cache counters so you can monitor how much cache is actually being read and written to the drive.

Click Start, and type this command


Windows Performance Monitor

If you’re view looks different, make sure Performance Monitor is selected in the tree in the left pane.

By default, perfmon monitors CPU processor time.  So that red squiggly line above shows my processor time, but I don’t care about that for ReadyBoost so let’s make this more useful.

Click the Red X button to delete the Processor Time counter.

Don’t worry you won’t break anything by doing that.

Next click the Green + (plus) button and browse for ReadyBoost Cache in the left list box.  Select it, click Add >> and then choose OK.

ReadyBoost Cache Counter in Perfmon

Now you can monitor ReadyBoost.

ReadyBoost output in Performance Monitor in Windows 7

Now  I’ll be the first to admit this is almost as easy to read as converting Hexidecimal to Binary in your head.  It probably looks no more legible than a kindergartener scribbling on a white sheet of paper with every crayon in a Crayola box.

It’s pretty cryptic so let’s make things easier to read by unchecking superfluous counters.

For example, all we really care about is the amount of ReadyBost cache being used to transport data.  So uncheck everything except Cache reads/sec and Cache read bytes/sec.  You should also scroll down and check Skipped reads/sec and Skipped read bytes/sec so you can see how frequently ReadyBoost is using your hard drive to read cache data.

ReadyBoost Revant Perfmon counters

Next, grab a huge file (or a bunch of files) and start copying stuff and pay attention to the amount of data being read from the hard drive cache verses the ReadyBoost cache; the two should be almost equal.

The Bottom Line

ReadyBoost isn’t the panacea for a slow computer.  Speed improvements do happen but don’t expect it to fill you with so much glee that you rhapsodize to all your friends about your new discovery.

ReadyBoost really shines on older computers with slow hard drives and low Windows Experience Index scores.  If you’re trying to breath new life into an old clunker give ReadyBoost a shot because it just might be all you need to make it useable again.


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Posted in How To, What Is, Windows 7 Tagged with:
  • Unicycle

    I just put a 32GB SSD into my computer which has otherwise a 5400rpm HD and a WEI of 4,6. It seems to me, Readyboost could help to improve this machine. However, I don’t find a way to enable Readyboost *on* this SSD. Any idea?

  • Akat Suki

    Nice post, thanks pro