, they find that more than 70% values in a program are short lived. In some cases, the short-lived values even let allocated registers never be referenced once after the instruction issue stage. In this case, because most consumer instructions nearby the producer have already read out that value from the ROB, it is possible that the register keeps a useless value for a long time without any references. The second type occurs when a register stores a temporary value which is no longer to be used or may be referenced again but after a long time. First, between the instruction issue stage and commit stage, the register does not store useful values, but waits for instruction commitment, thus waste static energy/power. Veljko Milutinović, in Advances in Computers, 2015 Idle Register File DVSĭuring program execution, RF dissipates two types of static power. If an argument is passed to the command return, it is used as the return value of the function: Return from a function: cancel the execution of the current function from the current position. The next run control command (run, continue, step, next) will execute from this new program counter address:Ĭontinue at a different address: resume execution at the specific line or at specific address:
Modify the execution address: the program counter is modified. Ĭhange the value of a local or global variable: assign 11 to variable “i”:Ĭhange the memory: set value 37 to the memory 0xbfc45400, converted to int:.The program execution can be changed in the following ways:
PC processors have multi-byte instructions, which are stored in multiple 8-bit locations, and use complex memory management techniques to speed up program execution. The operating system, the application program and the user data are stored in different parts of RAM during program execution, and the application program calls up operating system routines as required to read in, process and store the data. The address of the next instruction is then output and the sequence repeats from step 2. In the meantime, the program counter has been incremented (increased) to the address of the next instruction code. The result of the operation is stored in a data register (7), and then, if necessary, in memory (8) for later use. Additional data can be fetched from memory (6). The instruction execution continues by feeding the operand(s) to the data processing logic (5). The operands (code to be processed) are fetched (4) from the following locations in RAM via the data bus, in the same way as the instruction. The CPU then decodes and executes the instruction (3). The CPU reads the instruction from the data bus into an instruction register.
The instruction code is returned to the CPU from the RAM chip via the data bus (2). The address bus also connects directly to the RAM chip to select the individual location, giving a two-stage memory location select process. The address decoder logic uses the address to select the RAM chip that has been allocated to this address. The sample address is shown in hexadecimal form (3A24) in Figure 1.7, but it is output in binary form on the address lines from the processor (for an explanation of hex numbering see Appendix A). The CPU outputs (1) the address of the memory location containing the required instruction (this address is kept in the program counter).