Page Cross Danger, Effective Address Overflow Check
Original Publication Date: 1988-Mar-01
Included in the Prior Art Database: 2005-Feb-14
A mechanism efficiently identifies operands crossing virtual address page boundaries and segment identifier (SID) (64K byte) boundaries. The IBM System/38 (S/38) is supported by an internal processor interface called IMPI. Instructions at this interface, for the purposes of this article, are similar to the hardware supported instructions on the IBM System/370. These instructions are interpreted on the S/38 by Horizontal Microcode (HMC). Before the actual execution of most S/38 IMPI instructions begins, a check must be made to ensure that all of the operands are present in main store. If any portion of any operand is not present in main store, a page fault exception is taken and the instruction will be restarted (from the beginning) after the necessary page has been read from DASD.