RC2 ALU

Day 25

     The Largest departure between the HP and RC2 computers is definitely in the ALU itself the RC2 has a much larger instruction set and can carry out several more base functions as such this all adds to the overall complexity of the design but also helps to drastically improve functionality. What the HP can complete in a dozen clock cycles the RC2 can complete in 6 or fewer depending on the particular functions. This example is a perfect showcase for the evolution of modern computing and Moore's law in action using more modern techniques and customized components not only did the speed increase greatly but so did the complexity and usability.

      The HP computer ALU consists of a full adder a logic block an incrementer and a left shift register but not much else. The RC2 has all the same functions but can carry out functions such as NOT or SHIFT on both registers not just 1 also the SHIFT functions go either right or left which drastically reduces cycle count in the case of a RIGHT SHIFT. The SHIFT can also be manually selected between circular or non-circular shifts. The RC2 also features a CONSTANT function that as of yet I have not seen in the HP computer but would drastically assist with reducing cycles and memory accessing.

     I intend to spend some time studying the texts on both more in depth tomorrow and ferreting out more of the differences and to see what if any modifications I may wish to start designing into my build. Monday, however, I intend to move back to the clock circuit and walk through its operation with the schematic I drew up. Wednesday we will return to the RC2 build and what we can learn from it.