General Purpose Processor
The design of a general purpose processor or microprocessor builds a Programmable device that is suitable for a variety of applications to maximize the number of devices sold.
The features of such processes are
1. Program memory
2. Data path
The design of such a processor does not know what program will run on the processor, so the program cannot be built into the Digital circuit.
The data path must be general enough to handle a variety of computations, so such a data path typically has a large register file and one or more general purpose arithmetic (ALU).
The figure shows the simple architecture of a general purpose processor implementing the array summing functionality.
The functionality is sorted in the program memory. The controller features the current instruction as indicated by the program counter PC into the instruction register IR. It then configures the data path for this instruction and executes the instruction. It then determines the next instruction address, set the PC to this address and fetches again.
Time to market and NRE cost are low because the designer must only write a program but not do any digital design.
Flexibility is high because changing functionality requires changing only the program.
Unit cost may be low in small quantities compared with designing our own processors.
Performance may be fast for computation-intensive applications.
Design Matric drawbacks:-
Unit cost may be relatively high for large quantities.
Performance may be slow for certain applications.
Size and power may be large due to unnecessary processor hardware.
A general purpose processor, sometimes called a central Processing Unit CPU or a microprocessor. It consists of a data path and control unit, tightly linked with a memory.
The general purpose processor basic architecture consists of
1. Data path
2. Control unit
1. Data path:-
The data path consists of the circuitry for transforming data and for storing temporary data.
The data path contains ALU capable of transforming data through operations such as addition, subtraction, logical AND, logical OR, inverting and shifting.
ALU also generates status signals, often stored in a status register, indicating particular data conditions. Such conditions include indicating weather data is zero or whether an addition of two data items generates a carry.
Data path also contains registers capable of storing temporary data. Temporary data may include:-
1. Data brought in from memory but not yet sent through the ALU.
2. Data coming from the ALU that will be needed for later ALU operations or will be sent back to memory and data that must be moved from one memory location to another.
3. The internal data bus carries data within the data path while the external data bus carries data to and from the data memory.
The processes are distinguished by their size, usually size is measured as the bandwidth of the data path components. An N-bit processor may have: