Original post by: Dan ,
This series used the internal thermal sensor within the drive. Apple had three different cables to match up with the different vendors drives they used. To make this simpler I would just order this: [https://eshop.macsales.com/item/OWC/DIDIMACHDD09/|OWC In-line Digital Thermal Sensor for iMac 2009-2010 Hard Drive Upgrade] it will allow you to use any drive you choose. As to the drive: You've picked the best one for the upgrade! This system has a SATA II (3.0 Gb/s) drive interface so you do need to be careful you get a drive which is compatible (no problem here with the Seagate SSHD drive).