In a message dated 7/24/2007 10:56:09 A.M. Central Daylight Time, [EMAIL PROTECTED] writes: >very bad idea in general. if the page is not protected, then you don't know what other processes are updating that page nor how they serialize their updates. the OI is not an interlocked update and may cause corruption when another CPU is concurrently modifying that byte. OK. Find some other instruction that will not corrupt storage by serializing properly on the storage and which instruction will NOT really change anything in the storage. My main idea was to execute an instruction that does not really change anything but yet the instruction processing microcode tests the byte to be accessed for write capability in that page. I do not understand how my instruction that does not change any of the 8 bits in a byte can possibly corrupt any bytes anywhere near that one byte regardless of what other CPUs or I/O operations are doing concurrently. Here's another bad idea: find the page table entry for the page in question and test the page protect bit in that entry. Bill Fairchild Plainfield, IL
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