How can millions transistors be in a single processor?

Answer 1

Thanks to the wonderful technology we now posess, a single transistor can be constructed out of two thin layers of material (P-doped and N-doped), and can be very, very small - as small as a few atoms, as some researchers have proved not too long ago! Therefore it is easy to put many such small transistors - in layers - on a small chip - the processor. Many of these, in mass production, have these transistors constructed on the micron scale (typically around 15 microns). If a transistor is 15 microns wide, you can put 66 of them in a milimeter, on just one layer, many of which construct a single processor die. It is now typical to have not millions, but billions of transistors on a single CPU!

Think about it: if you can put 66 transistors in a 15x15 micron area, you can fit about 11 108 889 (11 million) of them in a 5x5cm chip - and that's just one layer about a micron thick? Assuming the die itself is 4x4cm and is 3mm thick, each layer is 2 microns thick, and each transistor takes a 21x21 microns of space on a layer --- on such a processor die you would fit 5 442 175 500 - 5 and a half billion transistors.

Of course, these transistors switch very small currents - very small indeed! Your typical, run-of-the-mill discrete transistor can handle much larger currents, and its bulky body is designed to dissipate the heat generated in the process, as nothing else will cool it down. Processors usually have designated cooling methods (like radiators and fans) - without one, the temperature within one rises to "boiling" within seconds.