Boot drive.
There is a lot of misunderstanding about caching. Intel developed caching for clients and businesses that could not afford a large capacity ssd. Back when the concept was on the drawing board, Intel hoped clients and businesses would purchase a small 10Gb or 20GB for about $100.00. Microsoft Windows 7 and all software applications would remain on hard disk drives. The cache only produced a minor boost in hard drive performance. Intel hoped that once clients saw the slight performance boost they might be inclined to purchase a larger ssd for much better performance.
Intel also researched the size of the cache. Intel determined that a 60GB ssd was the point where it made no sense to use the ssd as a cache for a hard drive. Instead if you have a 60GB or larger capacity ssd, then Windows 7 and software applications should be installed on the ssd to take full advantage of the ssd capabilities.
Since you have a 60GB ssd, it makes more sense to install Windows 7 your applications and a couple of your favorite games on the ssd. The ssd performance boost is much higher than the hard disk drive performance increase.
Windows 7 will use up a somewhere around 20GB leaving room for a couple of most favorite games. Additional games can be stored on a hard drive. You can swap games when necessary. It is easy to do.