---

System Bus

---

• You have now learned how to construct a simple CPU and seen the internals of static memory (or SRAM - Static Random Access Memory)

  BTW, we did not discuss the dynamic RAM or DRAM. They provide the same (memory) function and to really understand them will require transistor-level knowlegde (Field-Effect Transistors - FETs). Also, DRAM uses "refresh" cycles due to leakage in the FETs. There are just too much Electrical Engineering details in the DRAM discussion and the net result of the discussion to the increase in the understanding of the computer is zilt, so I skipped DRAM.

• There is one more thing that you do not know about the computer:
  • How do the different devices inside the computer communicate with each other ?

• We will remedy that in a two part study:
  • First we study how the CPU communicate with the memory
  • Then we will study how the CPU communicate with an IO device

• We will study:
  • The system bus
  • The interrupt mechanism (this may feel weird to you at first)