General Flashcards
True or false, decreasing response time almost always improves throughput
true, changing one often affects the other
Performance_x
1/execution_time_x
X is n times as fast as Y
performance_x/performance_y = execution_time_y/execution_time_x
CPU execution time
time the CPU spends computing for this task and does not wait for I/O
wall clock time/response time/elapsed time
total time to complete a task, including disk accesses, memory accesses, I/O, OS overhead, etc
CPU execution time
CPU clock cycles * clock cycle time
How .to improve performance
reducing the number of clock cycles required for a program, or the length of the lcokc cycle
CPU clock cycles
Instructions for a program * average clock cycles per instruction (CPI)
CPU Time in terms of instruction count
instruction count * CPI * clock cycle time
or
(Instruction count * CPI)/Clock rate
First steps of instructions:
- send program counter to the memory that contains code and fetch instructions from memory
- Read one or two registers, using fields of the instructions to select the registers to read
Three instruction classes
memory-reference, arithmetic-logical, branches
How can ALU be used?
memory-reference instructions use it for address calculation; arithmetic-logical for operation execution; branches for comparison
multiplexor
logic element to chose among multiple sources and steers one of those sources to its destination
clocking methodology
defines when signals can be read and when they can be written
edge triggered clocking
any values stored in a sequential logic element are updated only on a clock edge
