Here's how and why you should consider a RAM upgrade. The model I most recently upgraded is a vintage inch iMac and although. How to instructions and video to upgrade the RAM in Late , Mid, Mid- and Late (Inch and Inch) Aluminum iMac models. Hi Guys, My iMac came with 4 GB RAM (2GB X 2) installed. My iMac has 4 slots and I'm currently using 2. On 8eyu.com they claim I can leave.