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Unix Version 7 - man page for phys (v7 section 2)

PHYS(2) 			       System Calls Manual				  PHYS(2)

NAME
       phys - allow a process to access physical addresses

SYNOPSIS
       phys(segreg, size, physadr)

DESCRIPTION
       The  argument  segreg  specifies  a process virtual (data-space) address range of 8K bytes
       starting at virtual address segregx8K bytes.  This address range is mapped  into  physical
       address	physadrx64  bytes.   Only the first sizex64 bytes of this mapping is addressable.
       If size is zero, any previous mapping of this virtual address  range  is  nullified.   For
       example, the call

	    phys(6, 1, 0177775);

       will  map  virtual  addresses 0160000-0160077 into physical addresses 017777500-017777577.
       In particular, virtual address 0160060 is the PDP-11 console located at	physical  address
       017777560.

       This call may only be executed by the super-user.

SEE ALSO
       PDP-11 segmentation hardware

DIAGNOSTICS
       The function value zero is returned if the physical mapping is in effect.  The value -1 is
       returned if not super-user, if segreg is not in the range 0-7, if size is not in the range
       0-127, or if the specified segreg is already used for other than a previous call to phys.

BUGS
       This system call is obviously very machine dependent and very dangerous.  This system call
       is not considered a permanent part of the system.

ASSEMBLER
       (phys = 52.)
       sys phys; segreg; size; physadr

					      PDP11					  PHYS(2)


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