Radeon HD 7640G Game Requirement Analysis
Radeon HD 7640G is an integrated GPU on the fast-middle-class Trinity CPUs.
It's based on the 32nm Terascale 3 architecture and offers 256 Shader Processing Units, 16 TMUs and 8 ROPs. The memory interface will depend on whether or not the laptop's system RAM is dual channelled (128-bit if so, 64-bit, if not) and the operating memory clock can be up to 800MHz (max speed supported by the CPU). The central unit runs at 496MHz and will go up to 685MHz in Turbo Mode. Expect a TDP of up to 35 Watt.
Its performance is slightly above Intel HD 4000 Graphics but below previous in series - Radeon HD 7620G, despite the naming, due to the lesser Shaders count which proves useful in most of today's modern games.
Some of today's modern games can be playable using the Medium preset though the low preset will have to suffice for most of them. Extremely demanding games (e.g. Crysis 3) are playable but with reduced frame rates.