Edit : My first post to blow up. Crazy.
In: Technology
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The opposite is true.
Think about factories you want to connect with roads. The longer the roads, the longer it takes you to travel them. So to make things (data in a CPU) go from one factory to the other, you want the roads as short as possible.
But, if those factories are too close together, pollution (heat in a CPU) becomes a problem. So the only way to have those factories closer together is by making them produce less pollution (heat).
Therefore there is the balance to cram everything on a CPU as close together as possible, but not so close that it overheats.
The explanations posted are good, but I love this question because the actual math is so easy to understand.
Start with how big a processor is, which is **like an inch or two across** right?
Then think about how fast they’re doing stuff. The fastest boast a “4.0 GHz” (Gigahertz), which is the number of operations they can do in a second. That’s **4 billion operations per second**.
But then how long does it take them to do a single operation? Quick conversion, it’s **200 picoseconds**.
Then, we know the speed of light right? c is about **300,000 km/s**.
So the question is, how far can light, the fastest thing around, travel in 200 picoseconds? It turns out, when you crunch all the numbers, the answer is **2.4 inches**. Once you remember that it’s not moving straight it’s gotta wind around in there, it’s easy to see why a processor can’t possibly be bigger than an inch or two across and still run that fast!
Not posting this comment to diminish what /u/RhynoD or others have already said, what they said is absolutely true. CPU manufacturers want them to be small, but not too small.
However, not all CPUs are the same size, and many higher-end CPUs are physically larger. In fact, the actual chip in consumer CPUs vary in size, even though the total size of the CPU does not. What you see the CPU is a bit of the printed circuit board (the little green board that contains all the connections between the chip and the rest of the computer) and the heat spreader on top. As the name implies, the heat spreader takes the heat generated by the CPU chip and spreads it out to improve cooling.
Under the heatspreader is the CPU chip itself. Even though the board and the heatspreader size doesn’t change, the chip underneath can vary. For example, [here is a size comparison between three different Intel CPUs](https://images.anandtech.com/doci/13400/9900K%20Mockup.jpg). The board and heatspreader remain the same size between all three CPUs. AMD and Intel have both decided on similar (although not the same) size CPU board/heatsink size just so both their low end and their high end CPUs of a generation can all work on the same motherboards and other products like heatsinks.
Their professional level CPUs, such as some of Intel Xeon or AMD’s Threadripper/EPYC CPUS have physically larger heat spreader/boards in addition to having massive chips. Part of the reason certain Xeon chips cost over ten thousand dollars is that large single-chip CPUs have high failure rates per /u/dale_glass comment, so they need to charge the price for a black market kidney to make their money back. AMD’s high end CPUs these days are actually a bunch of smaller CPU “chiplets” acting as a single CPU, which allows them pack a ton of CPU horsepower in a package you will only need to sell half of your kidney for.
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