*** UNIX MANUAL PAGE BROWSER ***

MEM(4) Kernel Interfaces Manual MEM(4) NAME mem, kmem, kUmem, mtpr, fineclock - memory and VAX processor registers DESCRIPTION Mem is a file that is an image of the main memory of the computer. It may be used to examine (and even to patch) the system. Byte addresses in mem are interpreted as physical memory addresses. References to non-existent locations return errors. Kmem and kUmem are like mem, but access kernel-mode virtual memory. KUmem promises that reads and writes will be done in two-byte quanti- ties; this is convenient for UNIBUS accesses. Mtpr accesses VAX internal processor registers. Each register is 4 bytes long; register n may be read or written at address n*4. Fineclock reads a high-resolution clock. Reading four bytes returns a 32-bit unsigned integer representing the number of microseconds since the epoch 00:00:00 GMT, Jan. 1, 1970, with high-order bits discarded. Mem, kmem, kUmem, and mtpr have minor device numbers 0, 1, 3, and 5. Fineclock is a separate driver; the minor device number is ignored. FILES SEE ALSO time(2) VAX Hardware Handbook BUGS Examining and patching device and processor registers may give unex- pected results when read-only or write-only bits are present. An attempt to read a nonexistent processor register returns 0 instead of an error. The fineclock counter overflows every hour or so. It is only as pre- cise as the hardware; hence it is inaccurate on a MicroVAX. MEM(4)