A Note on the Interruption of Extended Core Storage Transfers

In the Control Data 6000 system transfers between central memory and extended core storage may be interrupted through the issuance of an exchange jump by a peripheral processor. Reinitiation of the transfer requires that it be repeated completely rather than resumed at the point of interruption. The transfer process locks out the central processing unit (CPU), so an interrupted trahsfer results in lost CPU time. In this note an estimate of this time loss as a function of interrupt rate, transfer length, and transfer initiation overhead is obtained, as well as an estimate of the transfer length which minimizes lost CPU time.