Access time
From Computer History Wiki
In main memory, the access time (sometimes response time) is the time period between the start of a read access cycle, and the point in time when the data is returned to the requestor.
In DRAM memories, if the memory is in the middle of a memory refresh cycle when the request arrives, that can delay the memory's response - and thus the access time for that particular cycle.
For secondary storage, such as disks, it refers to the time between when the disk is asked to perform an operation on a given block, and when the operation begins.
