ATI Radeon HD 4000 Series discussion

[GoldenTiger]

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

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

I HIGHLY suggest you educate yourself before posting such claims that are technically impossible. What you describe is a shared architecture, not a CrossFire/SLI setup.