install windows 10 via bootcamp not on the main drive

I did repair my early 2009 mac pro 4.1; and after installing a gtx970 I did realize that I may use it also for windows gaming.

Although my main drive is just a boot for OSX, which is a 90 GB SSD drive; the rest of my home directory and application support is on a SATA mechanical drive. Is possible to install Windows 10 via bootcamp, on a drive that is not the main drive? I am running 10.11 (el capitan), which is the highest OS that my machine seems to be able to run.