There is a AGPGART in 2.6.x . I presume that Mandrake has built it in. I haven't installed Mandrake in more years than I wish to admit ;-)
If you are using an Nvidia card with the Nvidia proprietary driver, they supply the GART.
I don't have an ATI card and can't speak to their implementaion in their proprietary graphics driver.
You might check your graphics card's web site to see what drivers exist. ( www.nvidia.com
Keep plugging along - bit of a learning curve but good brain food and a reliable system (no BSOD's !)