Originally Posted by parsec
Your reinstall of Win 8, what did you do to prepare the 840 first?
Your new installation likely has caused:
Windows Write caching to be disabled, which seems to be a bug with IRST. Find your 840 in Device Manager, and in the Policies tab, uncheck Write caching and click OK. Go right back in and check Write caching and click Ok.
Using the same power plan with the new installation?
Optimized the OS with the Magician software?
Same Windows indexing settings?
CPU speed and power saving options were identical for both benchmark tests?
How full is your 840? How much free space? Same amount of Over Provisioning on the SSD, if used?
A SSD's performance will not remain the same throughout its life. It will decline at a rate depending upon its usage, more writing done, more performance decrease. Usually seen more in write performance, which we see is your case. The only way to temporarily reset a SSD's performance is with a Secure Erase.
I wouldn't worry about the new firmware, which is available, it's not a performance enhancement.
The AHCI driver in Win 8 is new, called storahci. I'm not saying it's better than IRST.