Jun 21 2014

Building a CPU Part I – Implementing logic gates

For a long time now, I was thinking to myself: “I know how to develop softwares, And I also have a little bit of practice with drivers and compiling operation systems (I even tried to write my own code to a boot sector and run it), But I never really understood how CPU works”.

So I’ve decided to take matter into hands and try to build a CPU. At first I thought about creating it all from scratch, But quick enough I discovered that the amount of transistors I will have to solder is enormous (I will soon enough show that even a simple NAND gate requires 4 transistors). So I’ve decided to build it on FPGA which will make life easier, and instead of creating my own architecture, I’ve decided to try and mimic the 6502 microprocessor, which is the CPU used by NES. If everything will go according to plan, I will be able to play Super-Mario on my own CPU.

The first post will have nothing to do with FPGA, as logic gates are provided out-of-the-box when using FPGA, so this part will have nothing to do with my implementation of the 6502 microprocessor. But according to my belief this part is the most important one, because the logic gates are the basic building blocks of any electronic device, in particular a CPU.

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