I have to disagree with you. Having onboard video has nothing to do with dual channel. An add-in AGP card will be able to benefit from dual channel as well.
In very simple terms;
- Memory modules are accessed through a single channel (or connection) between the MCH (Northbridge) and the memory modules.
- In dual channel mode the memory controller reads from or writes to two memory modules, each on seperate channels, simultaneously.
a 64-bit 800MHz FSB offers at most 6.4GB/s of bandwidth between the Memory Controller Hub (MCH aka North Bridge) and the CPU..... .......to maintain bandwidth balance, the 875P's dual channel DDR memory controller supports DDR400 which, when installed in pairs offers the same 6.4GB/s of bandwidth as the chipset's FSB.
The benefits of Dual channel vs Single channel:
Quake III Arena=7.7%, Jedi Knight 2=9.6%, Comanche 4= 5.7%, etc.