Do you mean that you aren't getting the speed you want/hoped for from the drive or that a tool like Intel Rapid Storage Technology (found on my computer; click Manage, then open Advanced) reports the interface is connected at 3Gb/s. This tool or something similar should, I think, report 6Gb/s. Some tools (thinking of HWiNFO64) just report the drive's interface, not the actual negotiated speed.
For what it's not worth, I own one of these hybrid drives, but I found that its underlying mechanism is slower than competitors (based on benchmarking) and my use of it (as a storage drive -- I boot and run apps from a mSATA SSD) did not take advantage of its flash cache, so it's now in my child's notebook where it's serving its optimal purpose as a boot drive
. I guess all that means is I can't check whether would connect at 6 or 3 on my W520. Never thought to check while I was using it, sorry.
(The ultrabay is port 1 and also should offer 6Gb/s SATA III speed. mSATA is port 2; eSATA on W520 is port 3; eSATA on dock is port 4... ports 2+ are SATA II.)