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Annotation of 43BSDReno/share/man/man4/man4.tahoe/mem.4, revision 1.1.1.1

1.1       root        1: .\" Copyright (c) 1986 Regents of the University of California.
                      2: .\" All rights reserved.  The Berkeley software License Agreement
                      3: .\" specifies the terms and conditions for redistribution.
                      4: .\"
                      5: .\"    @(#)mem.4       6.2 (Berkeley) 6/30/87
                      6: .\"
                      7: .TH MEM 4 "June 30, 1987"
                      8: .UC 7
                      9: .SH NAME
                     10: mem, kmem, vmem \- main memory
                     11: .SH DESCRIPTION
                     12: .lg
                     13: .I Mem
                     14: is a special file that is an image of the main memory
                     15: of the computer.
                     16: It may be used, for example, to examine
                     17: (and even to patch) the system.
                     18: .PP
                     19: Byte addresses in
                     20: .I mem
                     21: are interpreted as physical memory addresses.
                     22: References to non-existent locations cause errors to be returned.
                     23: .PP
                     24: Examining and patching device registers is likely
                     25: to lead to unexpected results when read-only or write-only
                     26: bits are present.
                     27: .PP
                     28: The file
                     29: .I kmem
                     30: is the same as 
                     31: .I mem
                     32: except that kernel virtual memory
                     33: rather than physical memory is accessed.
                     34: .PP
                     35: The file
                     36: .I vmem
                     37: allows access to the mapped portion of the VERSAbus
                     38: i/o space.  On the Tahoe the upper megabyte
                     39: of the physical address space is accessible through
                     40: this file (0xfff00000 through 0xffffffff). 
                     41: Accesses to the upper 64 kilobytes of
                     42: the i/o space result in VERSAbus transfers with a
                     43: 16-bit address (the offset in this region) and a
                     44: ``non-privileged short i/o'' VERSAbus address modifier.
                     45: Accesses to the remainder of the mapped region,
                     46: result in VERSAbus transfers with a 24-bit address
                     47: and a ``non-privileged standard'' VERSAbus address
                     48: modifier.  This region is actually part of the region
                     49: between 0xfeff0000 and 0xffff0000
                     50: which generates VERSAbus transfers with a 24-bit address.
                     51: Accesses to the remainder of the one gigabyte i/o space
                     52: generate transfers that utilize a 32-bit address with
                     53: a ``non-privileged extended'' address modifier.  Any
                     54: 32-bit address generated by a cpu access to this part
                     55: of the i/o space have the upper two bits zero; thus,
                     56: for example, an access to physical address 0xfe000000
                     57: causes the address 0x3e000000 to be supplied in the
                     58: resultant VERSAbus read/write cycle.
                     59: .PP
                     60: On the Tahoe, the 
                     61: per-process data for the current process
                     62: begins at virtual address 0xbffff000.
                     63: .SH FILES
                     64: /dev/mem,
                     65: /dev/kmem,
                     66: /dev/vmm
                     67: .SH BUGS
                     68: Memory files are accessed one byte
                     69: at a time, an inappropiate method for some
                     70: device registers.

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