Yes is running on SATA 3 but i have installed SSD Drive* to it and have it setup as the startup disk.
*Cloned all the files from SATA to SSD
I hope it will not lag if i upgrade to macOS Sierra.
iMac Storage by Christopher Yeo
Just go ahead.
I hardly notice any differences esp with SSD installed.
SATA3 (R/W in 500MB/s) and PCIE SSD (R/W in thousands) differs greatly only in sequential R/W. Day to day use e.g. boot up, app launch has no noticeable differences.
