Multiple surfaces in SDL and OGL?

[SOUR-Monkey]

I'm using OpenGL in SDL, and I'm trying to super-sample my frame. This means I need to render to Surface1 (ie. all my OGL calls affect Surface1) and then scale that down to fit onto Surface2, which is then displayed on the screen. I haven't yet found a way to specify which surface is affected by the OGL calls and which is drawn onto the screen, though.

Does anyone know how to do this?