Radeon HD 6870M is a high-end GPU based on the 40nm Terrascale 2 architecture.
It's based on the Juniper Core (therefore related to Radeon HD 6770) and offers 800 Shader Processing Units, 40 TMUs and 16 ROPs on a 128-bit memory interface of fast GDDR5. Its central clock runs at 675MHz and the memory clock operates at 1000MHz.
Despite being based on the same Core used on Radeon HD 6770, its performance is more comparable to Radeon HD 6750 due to being heavily underclocked.
Using a 720p resolution, most of today's games are playable at high settings but some will require further reduced settings to be played optimally.