Early Castout Bit
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
A method of reducing the vulnerability of data in a store-in cache to parity errors is described below. A cache replacement policy intermediate between store-in and store-through has been described in [*]. In this scheme, each changed line is written back to main memory when it changes replacement status from MRU (most recently used) to non-MRU. This ECO (early castout) replacement policy has the advantage that changed data is resident in the cache for a shorter period of time and is therefore less susceptible to errors and untimely castouts due to cross interrogates; however, it has the disadvantage that the write-back traffic to memory is increased. The benefit obtained by ECO accrues almost entirely to lines that are ECO only once or a few times.