Just want to clear something up for SLI

a1r80rn3

Honorable
Jan 7, 2014
20
0
10,520
Hey guys,
I'm a long time AMD-ATI fanboy and I've just built my first Intel-Nvidia pc. I've used the Radeon compatibility matrix to figure this stuff out before. I know I can use two of the same cards with different amounts of RAM, but what is the actual drawback of using say a 660 3gb DDR5 with a 660 2gb DDR5. Just to make sure my 3gb card will only be able to use 2 out of the 3 gigs.

TL;DR:
2 GTX 660s
1 is 3gb
1 is 2gb
total is only 4gb sli, right?