Instructions per second

Instructions per second (IPS) is a measure of a computer's processor speed. For complex instruction set computers (CISCs), different instructions take different amounts of time, so the value measured depends on the instruction mix; even for comparing processors in the same family the IPS measurement can be problematic. Many reported IPS values have represented "peak" execution rates on artificial instruction sequences with few branches and no cache contention, whereas realistic workloads typically lead to significantly lower IPS values. Memory hierarchy also greatly affects processor performance, an issue barely considered in IPS calculations. Because of these problems, synthetic benchmarks such as Dhrystone are now generally used to estimate computer performance in commonly used applications, and raw IPS has fallen into disuse.

The term is commonly used in association with a metric prefix (k, M, G, T, P, or E) to form kilo instructions per second (kIPS), mega instructions per second (MIPS), giga instructions per second (GIPS) and so on. Formerly TIPS was used occasionally for "thousand IPS".

Computing

IPS can be calculated using this equation:

IPS

=

sockets

×

cores

chip

×

clock

×

Is

cycle

{\displaystyle {\text{IPS}}={\text{sockets}}\times {\frac {\text{cores}}{\text{chip}}}\times {\text{clock}}\times {\frac {\text{Is}}{\text{cycle}}}}

However, the instructions/cycle measurement depends on the instruction sequence, the data and external factors.

Scaling units

For the most early 8-bit and 16-bit microprocessors, performance was measured in thousand instructions per second, or kilo instructions per second (kIPS).

The term "mega instructions per second" became useful in the late 1970s.