Hecatoncheires is reportedly the codename of ATI's next-gen DirectX 11 architecture that will be released by the end of 2010. Little is known about this architecture but it is said to be a brand new design and not just an improved version of the RV870. The codename stems from Greek mythology, the Hecatoncheires were three giants of incredible strength and ferocity that helped overthrow the Titans. These mythical creatures were enormous in size, and each of them had one hundred hands and fifty heads.
In ancient Greek, Hecatoncheires means "hundred armed" and from what we hear this is a brand new architecture and not just improved version of R770, something that RV870 is.
There will be six other Greek names to take a place of three desktop and three mobile chips and they should be ready in late 2010.