If you want to really understand how a computer works, one of the best ways to do that is to build your own. Modern computers are orders of magnitude more complex than the comparatively simple computer-in-a-keyboard machines of yesteryear, so many people that want to tackle this challenge build retro computers reminiscent of the machines available in the 1970s and 1980s. Retro computers also hold sentimental value for those that grew up during the early days of the personal computing revolution.
Hardware hacker Igor has built a very refined retro computer, called the CRISS CP/M, that also incorporates some modern conveniences. While retro hardware purists may object to Igor’s strategy of using modern components, you would not know there was anything modern in the case by using the computer. It can emulate the hardware of the TRS-80, Microbee, Kaypro, or Robotron 1715 perfectly.
The completely open source design of the computer makes use of modern Microchip microcontrollers — the ATmega1284P emulates a Z80 CPU, an ATmega328P stands in as a peripheral controller, and the VGA controller makes use of ATmega328P and ATtiny13 chips. One of the modern conveniences is a ENC28J60 chip that serves as the Ethernet controller. 64 kilobytes of RAM is included. All chips are in DIP format, which makes it easier to trace signals and understand the inner workings of the computer, and also adds to the retro feel of the machine.
The monochrome VGA can display up to 80 by 25 characters, with five different character sets to choose from. A 160 by 96 pixel graphical mode is also available. With the CRISS CP/M running CP/M 2.2 right out of the box, a slew of programming languages, text processors, games, and business software can be used. For loading all of this software, there is another modern convenience available — an SD card reader provides the computer with mass storage.
If you are concerned about the dangers of retro computing, rest assured, Igor makes it clear that CRISS CP/M is “the SAFEST computer in the world.” I think something may have been lost in translation there, but in all seriousness, this looks like a very well thought out, and highly polished build. For those that are interested, kits and assembled computers are available.