Early Computer Designs with a concepts of SAP 1
In general design, most common computer systems has architecture of having shown in Figure 1.0. In this figure the Central Processing Unit (CPU), Memory, Input and Output devices are the main core of a computer system.
As defined in Wikipedia, CPU is the portion of a computer system that carries out the instruction of a computer program stored in the memory. The memory use as a storing data, then the data and information will transfer to the CPU. It will transfer in the outside world via input and output devices.
The CPU is the heart of its core; it has the more complicated part of all. It has two parts, one is the arithmetic and logic unit (ALU) and the second one is the control sequence/unit (CU).
In this concept we can relies in the Architecture of SAP 1 (Simple As Possible 1). In SAP 1 the design is just like the concept on Figure 1 of transferring information, data and instruction code. The only difference that in SAP1 there are more additional components and it is more specific in transferring data.
SAP1 has 10 components which are:
1. Program Counter (PC)
2. Memory Address Registers (MAR)
3. Random Access Memory (RAM)
4. Instruction Register (IR)
5. Controller Sequencer (CU)
6. Accumulator (A)
7. Adder-Subtracter (ALU)
8. B-Registers (B)
9. Output Register
10. Binary Display
SAP1 architecture contains 16x8 random access memory which is read only. This means that there are 16 memory location with 8 bits in each location. Each components has assigned address lines, just like the RAM which has a 8 address lines . SAP1 can only perform addition/subtraction and no logical operation. These arithmetic operation performs by the ALU which only has an adder/subtracter operations.
When an execution starts it is always start in the PC (which start always to 0). Its job is to send address to the memory . PC is always pointing to RAM. MAR allow us to send an address bits to the RAM. In this case PC will go first to MAR and the MAR is the one that send address bits to the RAM which allow us to store data memory before the program runs (see Figure 2.0). IR is part of control unit which can executes in two ways, the first is in 2 state output that directly go to CU while 3 state output which will go directly to WBUS. 3 state output used by an address or data. In 2 state output the IR will go to CU, Controller Sequencer (CU) controls the operation of the computer. Accumulator has 2 output also the 2 state and the 3 state output. The 2 state output goes directly to the adder/subtracter while in 3 state the output goes to the WBUS. B registers is a buffer register used in arithmetic operation. In the end of the execution the content of the accumulator s also the content of the output registers which is also the binary accumulator.
REFERENCE:
http://en.wikipedia.org/wiki/Microcomputer
http://hubpages.com/hub/A-Brief-History-of-the-Micro-Computer
