how much ram is cacheable with amd athlon

anybody know how much system ram the athlon thunderbird can effectively cache. like the intel vx and tx chipsets could only cache 64 megabytes of ram. The hx chipset could cache much more with a tag ram upgrade. are there similar issues with the athlon and its chipsets. anyone know. I couldn't get a serious response from AMD. i'm trying to figure out what to do and the clock is running out on present low memory prices. please help. thanks. bye, roy