On Thu, 9 Dec 2010 12:33:54 +0000, Bill Fairchild wrote: >You represented bit 31 incorrectly.... >It should be xxxxxxxx_8xxxxxxx. Bit 31 can be on in virtual >addresses above xxxxxxx1_00000000 (e.g.,12345678_9ABCDEF0),
right. >but any addresses between 00000000_7FFFFFFF and >00000001_00000000 will cause a program interrupt. It will produce a segment exception or a region-third exception if the appropriate invalid bit is on. It will not produce an addressing exception. >IARV64 will return only valid addresses when asked to get >new storage above the bar. Yes, but addresses from X'80000000' to X'00000001_00000000' _are_ valid addresses. However, IARV64 will not return addresses within that range. This has been discussed here before. Search the archives. If the OP's understanding were correct, it would be impossible to acquire a contiguous area that is 4GB in size. -- Tom Marchant
