If you don't know what this means or why you would want to do this, then check out the thread on XDA here
The thread is full of users trying various scripts to apply this every time the device boots as the settings don't stick, but Tasker makes this very easy for us…
You'll need to be rooted and install the free locale execute plugin prior to running the task.
To test if you are making improvements to your SD card's speed, SD Tools is a pretty good free application to use.
This profile is stand-alone and set to run on device boot. If you have another profile that is triggered in the same way, you can always delete this individual profile and then add a 'perform task' action somewhere in a current task to run SDCacheBoot
I'm not going to set up a separate thread for this, but you can always hunt me down on XDA if needs be.
Hope it speeds things up for you!