Hi, I'm pretty new to this stuff, I was just wondering if anyone could tell me how to make my own microcontroller. I have an old modem for dial up internet and a digital clock/radio to work with. Thanks
You'd need a microprocessor, RAM, ROM, IO chips and some glue logic to make a "large micro controller" which is generally referred to as a microcomputer. A micro controller is just a microcomputer on a chip. You could also build the whole thing out of TTL logic chips: http://www.homebrewcpu.com/
And once you buy one, buy a programmer to go with it. Saves a lot of headache over trying to build your own programmer. There are plenty of cheap programmers out there currently that work really well. Once you decide on what microcontroller brand you want to use, people here can even help you pick out which microcontroller in that brand to use and what programmer to use with it!
THe correct question then would be "how do I wire up a processor (ie. a motherboard but smaller)?" If that helps you get the idea of the scope of the project. Sometimes we can mislead ourselves by phrasing the question differently.
Unless you have 2-4 billion dollars to build and equip a semiconductor fab you are not going to be making your own microcontroller. That was the bad news. The good news is that you can use an FPGA(field programmable gate array) to make one. In order to do the design you can use a combination of schematic capture, macrocells, and Hardware Description Language(VHDL or Verilog). Some companies like Altera even give you free tools. Hope you got a fast connection; Quartus 7.1 was a 780 Megabyte download. This rates to be a multiyear project so I guess you'd better get cracking.