Yep.
Yes i have an Asus 6600 agp 8x. My mobo is an old sokcet A one and it only has agp 4x. I run my 6600 in the 4x slot and it runs fine. I bet i would see more performance if it was in the full 8x, but not by much i was told. It works and it will just run at 4x, but no biggie it will still run like it is supposed to.