1. A method, comprising: partitioning a unified cache into a first portion of lines that only store copies of instructions retrieved from a memory, a second portion of lines that only store copies of data retrieved from the memory, a third portion of lines that store copies of either data or instructions retrieved from the memory; and modifying the partition of the unified cache in response to changes in a ratio of a replacement rate for instruction lines and a replacement rate for data lines in the unified cache and further in response to a current activity status of a device that implements the unified cache, the current activity status indicating whether the device is in a sleep mode.