Interesting article that's very appropros for Tom's HArdware. Personally, I'd rather go to an auto magazine for auto articles, but that's just me.
Anyway, here's a question I've yet to get answered. Intel / AMD / IBM / whomever create a brand new chip. So, how do they know it will work as planned? How do they get the basic chip code to work if the chip never existed before?
Let's go back in time. Intel creates the 8008. Who wrote the code that made the chip work without first seeing a working chip? Sort of a catch-22 in my opinion.
So the deal works like that: as we are now pretty much late in the CPU making/designing game, there are lots of capabilities. But in general you just ask yourself - what is CPU? The answer: it is piece of code and some kind of instructions embedded in silicon. So what you can do is you can simulate on PC how this piece of code will work, add some instructions, delete them, optimize them etc. while it is a software. I don't know how they debugged 8008 microcode, but it can be something similar.
Then there is a step of translating code into electrical scheme, meaning that you have to implement all these instructions in terms of logical elements made out of transistors etc. Here some elements have to be added because of the simple fact that microcode knows nothing about real life and electricity so some complementary circuitry (such as capacitors, electro-static discharge diodes, power pumps etc.) is added
Then, knowing what will be the technology used for the CPU manufacturing, electrical scheme is tranfered to physical layout of layers of semiconductors, conductors and insulators.
The question is - how you debug these steps. Usually designers have some simulation tools and there are companies, which make pretty cushy living out of selling verification software.
But nothing is finally proved until the design meets production fab and real silicon chip is manufactured. Then there are testers, which run specila tests on CPUs and according to the chip's response desision is made if everything is operating properly.
If yes - we are good and here you have your brand new shiny C2D/Athlon or whatever.
If not - see my comments on revisions and steppings. So it is pretty much iterrative process until all the bugs are adrressed.
Enjoy,
CousinVinnie