[citation][nom]foogoo[/nom]
I'd have to do some more research on weather or not the tech is there to make a single chip twice as powerful as the 580 or 6970 but i couldn't see why not. They already put 2 gpus on the same board. Why couldn't they just make a single gpu twice the size of these? If someone could explain why they couldn't id like to know.[/citation]
Sure. I'll use Nvidia as example, due to their woes with Fermi, but everything also applies to AMD as well.
A single wafer coming off TSMC has 416 "candidates" for a single GF110 chip. There are 3 billion transistors in a GF110 die. Which means that some of the transistors will be defective, in one way or another - not work at all, not able to work at a wanted frequency, or that specific transistor uses too much power and therefore overheats, etc. Not every chip will even exhibit problems, either. If you go back to GTX480/470/465, they all used the same GF100 chip, but, due to massive parallelism of video cards, the defective portion can be turned off, exactly what we see in those cards (coupled with the reduction in operating frequency). Now, to create a dual-580 chip, you need double the transistors needed originally, b/c all functional parts are doubled. But with doubling of the complexity of the chip, the chances of something going wrong quadruples, if it is 4 times as complex then the chances of failure are 16 times higher, etc. So, let say you are yielding 300 workable (as in "not completely unusable", some of these become GTX580, some become GTX570, depending on what dies are working 100% as intended) dies from those 416. Now the size of new chip also doubles. Wafer doesn't change, and we are left with a 213 new candidates, but instead of getting 150 workable dies (1/2 of 300) we are down to ~40 workable dies, far cry from 150 pairs of 580 dies. Cost of wafer is the same, but the yields drop from 70% down to 18%. Nvidia is making unprofitable GPU which still has the same power consumption/heat as 2 separate GPUs. End result: Gotta wait for a new manufacturing node to address power/heat issues, do a LOT of engineering, and then release a single-chip card with double performance. If you remember, HD5870 is almost exactly double the HD4870 in shaders, ROPs, performance (same 256-bit bus did not help performance, hence "almost"), but it took a new node to achieve.
Peace, hope it's not too much to read!