| 摘要 |
PURPOSE:To make it possible to take an area stretching over pages as an access unit and to improve the performance by providing a means which changes the number of bytes of access so that the access area exceeds the page, where the start address of a virtual memory device exists, when the virtual memory device is accessed across pages. CONSTITUTION:When the contents of an address register LAR 19 are between an address 4(n-1) and an address 4n, an 8-byte area 14 is accessed by an instruction TR 8 instructing the fetch of 8 bytes, and 8-byte data is stored in registers 18 and 17. If the address 4n is page boundary, the TR 8 is switched to a 4-byte access instruction by a request selecting circuit 20, and a 4-byte area 16 is accessed, and data is stored in the register 18. When test branch is established, a 4-byte area 15 is accessed and data is stored in the register 17.
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