ATI Radeon HD 4000 Series discussion

[ORBR]

Yes, but the exact same data is copied on each 256-bit bus, therefore it is not seperate and able to be "added together" and considered a "one wide bus".

this is false my friend
each chip write different data on its bus, and you're sure they read the same ONLY if they work on the same (doubled in each memory bank) framebuffer
with AFR they can read slight different assets

and with crossfire you have doubled not only bus and shaders, but buffers TOO, making the way the bus works more efficient

finally I can consider two 256 bit bus as powerful as one 512 bit bus