need memory syscall - (nf)

[beaucham at uiucuxc.UUCP]

#N:uiucuxc:29300011:000:347
uiucuxc!beaucham    Apr 28 22:52:00 1984

   Can someone refer me to a standard syscall (in version 7, 4.1) which
will allow special users to read/write from/to memory which the unix
system prevents normal users from using?  apparently this is used in
bitmapped memory graphics applications.
  
    jim beauchamp  allegra!harpo!uiucdcs!uiucuxc!beaucham
                   or    pur-ee!/