| 摘要 |
PURPOSE:To decrease a hardware amount and to attain low cost by executing the check for exceptional accessing other than segments in all instruction areas estimated for accessing in precedence over the execution of variable length instruction. CONSTITUTION:An instruction word read from a main storage device 1 is transferred to a central processing unit 2 and stored in the 1st-3rd instruction registers 11-13. A subtractor 3 subtracts an output value of a decremental number generator 29 from an operand length or an operand size. An output of the subtractor 23 is generated corresponding to the operation of a switch 26. An exception detecting device 50 specifies the segment by a base address and a segment descriptor including the base address and the segment size, uses the sum of the base address and the effective address as a virtual address and conducts decision of accessing other than segments by comparing the execution address and the segment size. |
