ReadyBoost Performance Test

ReadyBoost thumb drive

If you have a slow hard disk, ReadyBoost (see instructions for setting up ReadyBoost) offers a significant performance boost. In my tests, adding a standard USB flash drive to a computer with a WEI disk rating of 3.7 reduced startup time about 30%. Adding ReadyBoost to computers with a WEI disk rating of 5.0 or higher did not improve startup time, but might slightly improve performance after startup. Future “Enhanded for ReadyBoost” flash drives will probably make more of a difference.

Conclusion:  If you have an unused flash drive, plug it in and set it up for ReadyBoost. It won’t hurt. If you have a computer with a WEI disk rating of less than 4.0, adding a ReadyBoost flash drive offers good bang-for-the-buck. If you have a computer with a WEI disk rating of more than 5.0, ReadyBoost still won’t hurt, but it probably won’t give you a noticable improvement.

Read on for the technical details.

ReadyBoost creates a disk cache file (ReadyBoost.sfcache) of the size you specify on flash memory, which offers better performance for random reads than hard disks. The contents of this file are encrypted so there’s no easy way for me to see exactly what’s cached, but Vista uses the “SmartFetch” algorithm to figure out what should be stored there. It reads from the cache whenever it thinks it’ll be faster than the hard disk. The cache is only a copy, so you can remove it from the computer at any time without losing data.

I tested ReadyBoost with three computers and two flash drives. The computers:

  • Dell Latitude D600. WEI disk rating of 3.7. This is a four-year-old laptop with a 4200 RPM hard disk.
  • Dell Latitude D820. WEI disk rating of 5.1. This is a nine-month-old laptop with a 7200 RPM hard disk.
  • Systemax generic desktop. WEI disk rating of 5.5. This is a three-month-old fast desktop with a 7200 RPM hard disk.

The flash drives:

  • Lexar JumpDrive 1GB. This drive reduced startup time by 30% in the older Dell D600 laptop, from 59.3 seconds to 39.8 seconds. This laptop has a slow (4500 RPM) hard disk. On my faster laptop (with a 7200 RPM hard disk) it didn’t improve performance, and the activity light hardly lit during startup. It was accessed after startup on all computers, so no doubt it increased performance by a small amount in general usage.
  • 2GB Kingston 50x CF card. This card only passed ReadyBoost performance tests on the desktop computer when connected to the internal memory card reader. When connected via a USB 2.0 memory card reader, it was too slow. Unfortunately, it didn’t improve startup times on the desktop–probably because the desktop has a fast hard disk (7200 RPM) and because startup is mostly sequential reads, rather than the random reads that ReadyBoost is optimized for.

I tested each scenario three or more times (until results were consistent). When first attaching the ReadyBoost drive, I waited for Vista to pre-load the cache by watching the activity light and waiting more than ten minutes. Then, I rebooted a couple of times to make sure the SuperFetch algorithm knew which files needed to be loaded, and waited for the drive to be updated (the activity light flashed regularly).

Here are the startup times for the D600, the only computer that showed performance improvements:

  • D600 without cache (seconds): 60.0, 59.3, 59.3
  • D600 startup times with cache (seconds): 39.7, 39.8, 39.8

If you can get your hands on an “Enhanced for Windows ReadyBoost” flash drive, you’ll get better results. Flash drives are always slower than hard disk for sequential reads, so ReadyBoost only uses flash drives for random reads, where hard disks are slow because of the time required to move the read head around. No doubt, flash drives that are designed specifically for ReadyBoost will be optimized for random reads. This is in distinct contrast to my Kingston 50x CF card, which is optimized for sequential writes–the most important factor for digital photography.

Please leave comments describing your experiences with ReadyBoost.

24 Responses to “ReadyBoost Performance Test”

  1. Gary says:


    It seems this is a good way to test Readyboost’s performance,but I got a question.

    You wrote that you reboot several times until Superfetch works,as I know that superfetch figures out users behavior and speed up performance,is that why you reboot several times? I think the purpose is to reduce the effect superfetch interferes Readyboost’s testing.Is that right?

  2. Tony says:

    I rebooted several times just to make sure the results were reproduceable and consistent. As I recall, they were consistent right from the start.

    Vista will adjust the contents of the cache over time to your behavior, however.

  3. Gary says:

    Thank you Tony.

    No matter Readyboost is enabled or not,superfetech is always working right?
    Without readyboost, superfetch loads files that users frequently access from hard disk.If with Readyboost, superfetch can load files from flash drive instead of hard disk.
    Is my opinion right? Thank you for your time.

  4. Tony says:

    Gary, that sounds about right.

    SuperFetch is always working; it’s just a smarter algorithm for accessing files.

    ReadyBoost accesses files from the flash drive if, and only if, it’s faster to access it from flash memory than it would be from disk. Specifically, non-sequential reads.

  5. Gary says:

    Dear Tony,

    Thank you for your explanation.

    Another question is,you tested Readyboost performance by measuring startup time,but as I know , the flash drive can be only detected/accessed until Windows detects it.How does it improve startup time?Readyboost should not be enabled before entering Windows.

    Could you please check if following is another method to test Readyboost?

    1. Create a new account.
    2. Start Vista and login new account.
    (Above two are make sure that Superfetch hasn’t involved in)
    3. Run some application to fill in all available memory.
    4. Run Windows Mail and measure first startup time.
    5. Enable Readyboost.
    6. Close Windows Mail and run other applications to make sure that Windows Mail program is cleared in memory.
    7. Run Windows Mail again and measure 2nd startup time.
    (This time should be fast because of Readyboost)

    Is above an another good way to test readyboost performance?

    Thank you!

  6. Tony says:

    It’s definitely on my list to do some post-startup ReadyBoost testing–I can tell it helps some, even on my fast computers, because I see them accessing the ReadyBoost drive regularly. I probably won’t have time for at least a couple of weeks, because I have some very anxious editors :).

    ReadyBoost is designed to help startup time, but I don’t know exactly which stage it’s available. As you can see from my tests, it definitely does significantly help on computers with slower drives.

  7. loops says:

    How did u get a score of 3.7 of a d600…i have a d600 and my score is 1.0….d600′s only have a radeon mobility 9000 with 32mb of vid memory which scores 1.0 hence the lowest subscore on vista’s rating

  8. Pugwash says:

    Are you looking at the overall rating or just the Primary hard disk subscore?

  9. Eric Johnson says:

    I have the Patriot XPorter XT 4 GB flash drive and have enabled ReadyBoost for my laptop. I have one GB of RAM (that’s all this particular computer can go to). When I right-click Properties on the flash drive, and click the ReadyBoost tab, I can only go up to 1150 MB to reserve for system speed. I wanted to be able to use 2.5x of my RAM for this. Any idea why I’m limited, and/or how to increase this?

    Thanks. Great blog.

  10. Hozer says:

    Ready Boost is a JOKE!!! Its too Slow!!

    Lets do the math………….

    Fact 1: The maximum data transfer rate on a memory stick is 24-30mb/s MAX!!!!

    Fact 2: The data transfer rate on a hard drive is 80+mb/s

    As you can see that memory sticks are about 2.5 times slower than a hard drive.

    Told Cha!!! ;)

  11. Matt says:


    Pfff.. dude.. Readyboost is not about sequential reads.. its the accesstime that counts here!

    Please, read on how it works before you make lame remarks like this…

  12. Iwan says:

    Tony, i’m having a hard time trying to get ready boost to work on my laptop using 2 gig Sandisk Extreme III. I’ve search and found out that this card is ready boost certified. I also find out that problem could be from my internal card reader, how to solve this problem? I’m using VAIO VGN-TZ17GN, it has both memory stick pro duo and SD slot (it’s a Ricoh Device). I only have 1 gig Ram which is why vista is ‘walking’ very slow and all the more reason for me to make ready boost work. Thanks for your kind help.

  13. lewis says:

    Btw ppl if you use readyboost and want to hide the drive in my computer theres a registry hack that can do this.

    Open your registry and find or create the key below.

    The “NoDrives” value uses a 32-bit word to define local and network drive visibility for each logical drive in the computer. The lower 26 bits of the 32-bit word correspond to drive letters A through Z. Drives are visible when set to 0 and hidden when set to 1.

    If your not happy working in Hex, add these decimal numbers to hide the drive(s):

    A: 1, B: 2, C: 4, D: 8, E: 16, F: 32, G: 64, H: 128, I: 256, J: 512, K: 1024, L: 2048, M: 4096, N: 8192, O: 16384, P: 32768, Q: 65536, R: 131072, S: 262144, T: 524288, U: 1048576, V: 2097152, W: 4194304, X: 8388608, Y: 16777216, Z: 33554432, ALL: 67108863

    For example to hide drive A and drive D, you would add 1 (A) + 8 (D) which means the value should be set to “9″.

  14. lewis says:

    sorry should have given location:


  15. garlen says:

    hey guys i just got a flash drive which is enhansed for ready boost and i havent noticed any diffirence in any thing. u may say i may have really good ram (think again) i have 512mg of ram and i got a 2 gig flash drive and it did not do any diffirence. my laptop is still continuasly asking me to close programs every now and then and is still very slow. im not even sure if ready boost is working. even tho the flash drives light flash constantly. and if i went on task manager it still says i have 512 ram????? helppppppp

  16. DC says:

    It’s not like adding more physical RAM to your system… from my understanding it caches small temporary files which will benefit from random reads.
    Your system still uses the paging file on the hard disk, and will still require physical RAM to avoid paging to disk. I’d suggest buying more RAM.

  17. JNP says:

    I had an extra Kingston 2gb MicroSD card lying around that I put into the adapter and plugged into the front memory card reader on my HP TouchSmart IQ770. Not a screaming fast machine for sure, with only a Turion dual-core 1.6ghz processor and a total machine WEI of 4.6. The hard drive has a 5.8 WEI rating, though, so I didn’t expect much improvement. My TouchSmart has a built-in HD television tuner and DVR. Without ReadyBoost, the picture stutters for a moment when I do other tasks like change volume, etc. With ReadyBoost, all HD picture stutter is GONE! This 12 dollar microSD card is a nice, inexpensive little kick in the pants to my system! Haven’t had time to test other things like startup time, etc, yet.

  18. JNP says:

    My first post is right above this one. I finally had time to test my boot time with and without the 2gb ReadyBoost. Without ReadyBoost, my machine takes about 1 minute 30 seconds to boot. With ReadyBoost, my machine boots in less than 55 seconds! Like I said in previous post, nice, inexpensive kick in the pants for my system!

  19. Copy Editor says:

    Enhanded for ReadyBoost ?


    EDIT your articles before you publish,
    it is humiliating to have stupid mistakes!

    • One of my favorite things about blogging is that I don’t have to edit posts, and that lets me publish articles much faster. Most people are concerned about the content and don’t notice typos.

      BTW, your comma should have been a semi-colon. You suck as a copy editor.