Semiconductor & Computer Engineering
The iso- prefix is used to indicate that a given difference measurement (or estimate) is reported while maintaining one or more other parameter(s) fixed.
Overview
The iso- prefix means 'equal'. The word originated from îsos in Ancient Greek which had a similar definition. The prefix is used to denote that a certain reported difference measurement or estimate was done while maintaining one or more secondary parameters fixed. In other words, an iso-comparison isolates one parameter from a number of parameters that affect each-other.
iso-comparisons are important for when different parameters may positively or negatively affect the primary parameter being compared. For example, if a CPU core may deliver improved performance versus a predecessor by utilizing a more advanced process node or by making use of more advanced circuit design techniques or both. Using an iso-process comparison would demonstrate how much benefits came from the design alone.
Example
For example, "2nd-generation CPU core delivers 10% reduction in power at iso-performance and iso-process" means that the said 2nd-generation CPU core is able to achieve a reduction of 10% in its power consumption (under certain workload conditions) over the 1st-generation for identical performance level or capabilities on the same process node. In other words, this example highlights the circuit and architectural design improvements. This comparison isolates the power consumption of the core as a function of only circuit and architecture design improvements while intentionally ignoring the effects of using a different process technology.
Comparison types
- iso-performance - A comparison that is done at a fixed performance level (e.g., at a fixed SPEC CPU2006/17 score).
- iso-power - A comparison that is done at a fixed power level (e.g., 1W/core)
- iso-area - A comparison that is done at a fixed physical silicon area
- iso-frequency - A comparison that is done at a fixed frequency (e.g., at 2 GHz for all devices)
- iso-throughput - A comparison that is done at a fixed throughput (e.g., same memory or PCIe bandwidth)
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