Nanometer

[kilo_17]

Hey guys. Since I'm new to PC's and all, I was wondering about the whole "nanometer" concept. Does it mean the CPU core is manufactured at a size measured in nanometers, or is it the whole die manufactured at a certain size. Does the smaller the size mean a better, more efficient CPU, or does it not make that much of a difference (i.e. 45 vs. 32nm). One final question, how big is a nanometer? Thanks for all your input, like I said I'm new to PC's and all, so I haven't learned all this yet.

 

[hunter315]

The nanometer sizing they refer to is the length of the channel of the transistor(MOSFETs on wikipedia) Shorter channels allow for lower gate voltages and smaller currents which reduce the power consumption of each transistor. They tend to decrease in size by about 0.7, this lets them fit twice as many transistors onto a chip of the same size. They tend to manufacture CPU cores on large wafers, often about 300 mm in diameter so it doesnt matter how large the whole CPU die is as they make a ton of them at a time then cut them all apart.


As for how large a nanometer is, its obscenely small, a hydrogen atom is 0.1 nm in diameter, a red blood cell is ~7000 nm in diameter, so 45nm and smaller has no rational reference as you are down in the size of few thousand atoms and some really high frequency light.
http://en.wikipedia.org/wiki/Orders_of_magnitude_(length)

 

[kilo_17]

So nanometers actually have to do with the MOSFETs and not the CPU? And I'm guessing the channel of the MOSFET is where all the current goes through right?

 

[hunter315]

The CPU is built up of transistors, MOSFETs(Metal Oxide Semiconductor Field Effect Transistors) in particular, transistors are just little switches but when used right they can serve as memory too. The entire CPU is built out of transistors so that nanometer size still has to do with the CPU, its just a bit more specifically, what the CPU is made of.

The channel of the MOSFET is where the current flows through.

 

[kilo_17]

Okay. So then the shorter the channel of the transistor, the more efficient it is? Which would mean a 32nm chip would perform more efficiently than a 45 or 65nm chip, right?

 

[hunter315]

Efficiency requires something to compare it to. Transistors with shorter channels use less power, so if you took one chip and simply shrunk it down it would be more efficient, but generally , they make use of the ability to fit more transistors on the die to give more advanced archtectures which make more efficient use of the transistors, so each size drop tends to give you better performance and reduced power usage, not just reduced power usage, but yeah, in general a 32nm chip will be more efficient than a 45nm or a 65nm chip

 

[kilo_17]

Best answer selected by kilo_17.