I have Gigabyte GTX 770 4gb and Asus GTX 770 2gb version, Sli option isn't showing up in nvidia control panel, I have connected the sli bridge.
Motherboard : M5A99FX Pro R2.0
Unfortunately you can't mix a 2gb and 4gb card in SLI. AMD Crossfire, I believe, allows different ram cards to work but not Nvdia. There might be a hack or work around but I don't know it. Read this thread for more information. There might be a way to make it work but it doesn't sound like it is worth the hassle since stability becomes an issue. https://forums.geforce.com/default/topic/760860/sli-doesnt-work-/?offset=5
Unfortunately you can't mix a 2gb and 4gb card in SLI. AMD Crossfire, I believe, allows different ram cards to work but not Nvdia. There might be a hack or work around but I don't know it. Read this thread for more information. There might be a way to make it work but it doesn't sound like it is worth the hassle since stability becomes an issue. https://forums.geforce.com/default/topic/760860/sli-doesnt-work-/?offset=5