Electronic – How many transistors is a transistor connected to in a CPU

It's simple, we test them before we sell them and throw the bad ones out.

There are lots of ways to do this - different people do different thing, often use a combination of:

• some tests are at speed to make sure they go fast enough.

• other tests involve a mode that turns some or all of the flipflops in the chip into giant serial shift registers, we clock known data into those chains, then run the chip for one clock and then scan the new results back out and check that they match our predicted results - automatic test tools generate a minimum set of "scan vectors" that will test every random gate or transistor on the chip - other vectors do special tests of ram blocks,

• others test that the external wires are all bonded correctly

• we make sure it's not pulling an unhealthy amount of current

Testing time costs money, we sometimes do some simple testing for obvious dead chips before they are packaged to discard the bad ones and then more testing after the packaging is done

A detailed answer is not so much a company secret, but rather the subject of several semesters at a University. Don't expect to get a complete answer here.

One of the best books on the topic is this one: http://www.amazon.com/Computer-Architecture-Fifth-Quantitative-Approach/dp/012383872X/ref=ntt_at_ep_dpt_1

There are also numerous books on digital logic design that would be good to read as well.