I'm thinking of bying 1 or more flash drives or an SD card to use with the readyboost function on by 64bit Windows 7 machine. I have a few questions regarding it before i put my hand in my pocket and buy anything. If i go ahead I would be using the fastest available flash/SD.

I have 6GB of RAM current installed so will readyboost make any difference to boot / program load times?

Will 2 x 2GB flash drives be quicker than 1 x 4GB or is the limitation on the motherboard?

Would an SD card better than USB flash drive?


  • 1
    As Justin stated ReadyBoost is more suited for memory starved systems (i.e 1GB of memory or less) and has very little effect on systems with more memory. There is a related feature called SuperFetch which is built into windows and will try to precache commonly used programs when plenty of memory is spare. See tomshardware.com/reviews/…
    – Mokubai
    Feb 2, 2011 at 14:13

5 Answers 5


I've also been doing a little research on the same topic and this is what I came up with.

This is a quote from windows.microsoft.com

Here are some tips on what to look for when selecting a USB flash drive or flash memory card to use with ReadyBoost:

The minimum amount of available space recommended for ReadyBoost to effectively speed up your computer is 1 GB.

For best results, use a flash drive or flash memory card with available space of at least double the amount of memory (RAM) in your computer, and preferably four times as much memory. For example, if your computer has 1 GB of RAM and you plug in a 4 GB USB flash drive, set aside at least 2 GB on the flash drive to get the best performance gain from ReadyBoost, and preferably the entire 4 GB. How much memory you need depends on how you use your computer. Keeping a lot of programs open at once uses more memory.

Give ReadyBoost 2 GB to 4 GB of space for best results on most computers. You can reserve more than 4 GB of space for ReadyBoost on most flash drives and flash memory cards. (Storage devices formatted with the older FAT32 file system can't store more than 4 GB.) You can use a maximum of 32 GB of available space on any single removable storage device with ReadyBoost and up to 256 GB total per computer (by inserting up to eight USB flash drives or flash memory cards into the same computer).

To work with ReadyBoost, a USB flash drive must support USB 2.0 or higher. Your computer must have at least one free USB 2.0 port where you can plug in the flash drive. ReadyBoost works best if you plug the flash drive into a USB port directly on the computer, rather than into an external USB hub shared with other USB devices.

If you want to be sure a USB flash drive works with ReadyBoost, look for a note from the manufacturer that the flash drive is "Enhanced for ReadyBoost." Not all manufacturers list this on their packaging. If there is no mention of ReadyBoost compatibility, the flash drive still might work with ReadyBoost.

There are many different kinds of flash memory cards, such as CompactFlash and Secure Digital (SD) memory cards. Most memory cards work with ReadyBoost. Some SD memory cards don't work well with ReadyBoost due to issues with the SD card interface. ReadyBoost will display a warning message if you attempt to use one of these cards.

Now, on a personal note, I tried ready boost for myself on my laptop which runs Windows 7 (64-bit) with six gigs of RAM and an i5 processor.

I used a 32 gig SanDisk cruiser flash drive reformatted to ex–fat format so as to dedicate the entire flash drive to readyboost and I did notice that files open a bit faster than before. I tried opening some pretty large files and I can tell you that I definitely noticed that it takes less time than before.

So, my conclusion is that although my laptop has six gigs of RAM, dedicating that 32 gig flash drive to ready boost definitely was worth it. The thing is, I really don't want a flash drive sticking out of my laptop so I just ordered a 32 gig SanDisk SD card to see how that does because my plan is to leave it in permanently, I will keep you informed as to how that goes.

P.S. FYI, not every flash drive or SD card will work for readyboost, I tried a SanDisk Extreme SDHC UHS1 SD card with a [10] rating, suitable for advanced cameras and HD camcorders and it did not work with readyboost. I have now ordered a 32 gig SanDisk Ultra SD card which I believe would work because I've tried a two gig version of the Ultra that has a [4] rating and it worked great.

I will let you know if I was able to use the entire 32 gig SanDisk ultra for readyboost.

Remember, You can use a maximum of 32 GB of available space on any single removable storage device with ReadyBoost and up to 256 GB total per computer (by inserting up to eight USB flash drives or flash memory cards into the same computer).


ReadyBoost has the best effect on older systems that are on the low end of what the operating system supports. Newer systems generally don't see a huge performance boost.


I tried using a fast (class 10) 8GB SD card for ReadyBoost on my Win 7 x64 laptop. It booted very slightly faster, but overall I didn't feel it had much effect. I found the presence of a drive letter that I couldn't use for anything sort of annoying, so I stopped using it and don't miss it. I had a similar experience with Vista's ReadyBoost and a USB drive.

If I had spent money and bought the SD card explicitly for this purpose, I would have been disappointed.


I know this is incredibly old, but there's a lot of misinformation in here.

Readyboost is a caching system. it has nothing to do with memory usage. If you have an ssd or a screaming fast USB thumbdrive (usb 3.0 is crazy fast, even with low end sticks), and a slow main drive, what readyboost does is cache everything that you use most often onto fast storage.

This is not like ramcache, which gets purged on reboot. If you boot windows, load firefox/chrome, play a couple of games, you will see a HUGE boost in load times for those features regardless of how much memory you have. The absolute easiest way to increase performance in windows is to buy a cheap 32GB SSD and dedicate it to readyboost.

Intel even markets their mainboards and intel SSDs as a caching solution. You plug your intel SSD into a special sata port, and the mainboard hides it from your OS. in the background, it does a FIFO cache of your hard disks, with a bit of weighting on what you use most often. What this breaks down to is whatever you load the most often on your PC, be it iTunes, WMP, Chrome, Steam games, etc, readyboost and the intel caching do the same thing. After an initial check, the OS won't hit your slow mechanical spinny drive, instead using the cached content on the fast storage.

TL:DR Readyboost is a persistent filesystem cache. It is useful for everyone, including those with SSD boot drives.

  • 2
    Actually it is SuperFetch that uses ReadyBoost, not the other way around. ReadyBoost just allows SuperFetch to use the USB drive as additional storage. And ReadyBoost is not persistent across rhutdown/reboot. That is because Windows cannot trust that something hasn't corrupted the data on the USB drive between boots - the reboot is considered the same as if you'd pulled and reinserted the drive while Windows is running. The Ready_Drive_ cache, which is similar to ReadyBoost but uses NVRAM built into a hard drive (a particular type of SSHD), is considered persistent, but ReadyBoost is not. Sep 24, 2015 at 23:33

Despite the amount of RAM you have, ReadyBoost can still make a small improvement in the time it takes to load a program the first time after booting. After that, with 6 GB of ram, there will be pretty much no difference in load times due the the app being cached in memory.

The biggest differences will be noticed on systems with very little memory, but ReadyBoost still makes my system feel a bit snappier with a 750 GB 7200 rpm drive and 4 GB of RAM when multitasking.

Ultimately, if your system feels slow and you want a bit more responsiveness, it may be worth a try, but you can't expect a performance boost other than some minor load time reductions and possibly a slightly more responsive feeling computer.

Regarding your question of 2x2 or 1x4, there is probably very little difference, but if the cards are identical otherwise, the 2x2 might be a tiny bit faster. I understand that on Windows 7 ReadyBoost can use multiple cards to further improve performance. I would try get at least 6 GB of memory cards total though as Microsoft recommends that you have at least as much Flash storage as RAM.

  • 1
    ReadyBoost cannot make a difference in program load time the first time after booting. It is not persistent across boots. Sep 24, 2015 at 23:36

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