Type 'opera:config' into the address bar and press enter/return, then type 'SPDY' into the search box at the to of the page and see which SPDY options are ticked or enabled.
If you do make any changes and wish to keep them, you have to click the 'Save' button below each section of the options you change. Not clicking the 'Save' button will set the option back to the previous setting when you exit the preference editor.