I suspect you're a student of some sort, starting out in dealing with the world of engineering. So here's a bit of a lesson in engineering.
There's a bit of a hierarchy of design when dealing with things as complex as CPUs. It looks a little something like this (note, there is considerable hand waving and generalization in the statements below):
- A company like Intel or AMD has some really low level group that deals with a simple question like "how do we make a transistor that works at 4GHz?"
- When they've figured it out, they translate that knowledge to some kind of CAD tool that automatically designs the right kind of transistor and lays it out in the right place.
- That software is used by a group that deals with a slightly more high level question like "how do we make a 4GHz logic gate using our 4GHz transistor technology?"
- They then translate that into a CAD tool for higher level use.
- That is then in turn used by a group that deals with something like "How do I make an adder using our 4GHz logic gate technology?"
- That is worked into a high level CAD tool like VHDL/Verliog/various proprietary languages.
- There's a few more levels of abstraction here.
- So now, some architect at Intel/AMD can say "I want a CPU that executes an ADD instruction in 5 clock cycles at 4GHz, is fully pipelined and has a few bells and whistles", that can then get translated down the chain of engineers and CAD tools so that in the end, you come out with a CPU with billions of transistors without having to lay out each transistor individually.
This higherarchy can work both forwards and somewhat in reverse, that is a high level design concept drives a change in low level technology or a new low level technology can drive a change in thinking at a higher level. In a nutshell, that is engineering.
For specific commercial tools, look at the web sites of Synopsis, Cadence and similar companies. Needless to say, this software is insanely expensive because it's very specialized. You may note that someone like Synopsis has a lot of high level tools and some low level tools like Hspice that let you deal with individual transistors.
The moral of the story is that a hierarchy of abstraction makes engineering possible. The thing that allows an Intel engineer to design a CPU without having to lay out each individual transistor is the same as what allows someone to design a bridge without knowing how to pour concrete and to design a car without knowing how to grind metal gears (more or less, see below)
That said, there's always some leakyness in these abstractions and that's why you're taught a bit of everything as an engineer. Your high level design decisions may affect what choices are made at a lower level, and you are expected to be somewhat aware of what these are. The high level guy at Intel has to be somewhat aware of the fact that he can't just say "I wan't an processor that executes an ADD instruction in 1 clock cycle at 100GHz" simply because the low level guy will say it can't be done.
Cheers,
Chris