It is a known fact that over time processors (or chips) are becoming smaller and smaller. Intel and AMD are in a race for the smallest standards (45nm, 32nm, 18nm, ..). But why is it so important to have the smallest elements on the smallest chip area?
Why not make a 90nm 5x5cm cpu? Why squeeze 6 cores into a 216mm2 area? It will be easier to dissipate the heat from larger area, manufacturing will require less precise (and thus cheaper) technology.
I can think of few reasons:
- less size means more chips could be made on single wafer (but wafers aren't very expensive, right?)
- smaller sizes are important for mobile gadgets (but everyday PCs still use tower boxes)
- small size is dictated by light-speed limit, the chip can't be larger than the distance an EM field can travel in 1 cycle (but thats approximately several cm at 3GHz)
So, why do chips need to become smaller and smaller?
Best Answer
It's like candy bars. They keep making them smaller at the same price to increase profit.
Seriosly though, there are good reasons for smaller chips. The first and foremost is that more chips can be fit onto a wafer. For large chips, the cost is all about what fraction of a wafer it uses. The cost to process a wafer is pretty much fixed, regardless of how many chips result from it.
Using less of the expensive wafer is only one part though. Yield is the other. All wafers have imperfections. Think of them as being small but randomly scattered about the wafer, and any IC that hits one of these imperfections is trash. When the wafer is covered by lots of small ICs, only a small fraction of the total are trash. As the IC size goes up the fraction of them that hit a imperfection goes up. As a unreal example that nonetheless points out the issue, consider the case where every wafer has one imperfection and is covered by one IC. The yield would be 0. If it were covered by 100 ICs, the yield would be 99%.
There's a lot more to yield than this, and this is greatly oversimplifying the issue, but these two effects do push towards smaller chips being more economical.
For really simple ICs, the packaging and testing cost dominates. In those cases, the features size is not so much a driving issue. This is also one reason we have seen a explosion of smaller and cheaper packages lately. Note that extreme small features size is being pushed by very large ICs, like main processors and GPUs.