8 Bit Computer Architecture

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 This is a very simple 8-bit architecture with 7 registers and an accumulator for storing intermediate results. I call it, the Primis - which should be Latin for first - it being my first computer design. The pipeline is limited to two stages: The first to the accumulator and the second to the load function on the register array. There are no flags on the ALU for negative values or zeros, these could be added later; however, I'm happy with this design and I plan to move forward from here.

(8-bit CPU "Primis" - designed by James Reagan 2019)


Below is the architecture of the almost 45 year old Intel 8008. It is clearly more advanced than my simple 8-bit architecture. It has dynamic frequency scaling - which is basically automated overclocking to manage power and temperature; a properly designed "on-chip" stack; four conditional flags for zeros, parities, carries, and signs; it also sports a CLA adder whereas my CPU has a classic ripple-carry-adder. The 8008 had around 3,500 transistors. In comparison, the i7-8068k has around 3 billion transistors. which is 8 orders of magnitude larger.


I've also wanted to understand how each component operated using logic gates, so I designed a 4-bit computer with an ALU that has an adder and a few bit operations. The program counter is a MS-SR flip flop with a feedback (the simulation didn't work properly without it).
(4-bit CPU designed by James Reagan 2019)

Ken sherriff has a very detailed analysis of the 8008from die photos - http://www.righto.com/2017/03/analyzing-vintage-8008-processor-from.html
And most of the basic information about the 8008 was collected from wikipedia - https://en.wikipedia.org/wiki/Intel_8080

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