From: utzoo!decvax!harpo!seismo!hao!hplabs!sri-unix!greep@su-dsn.arpa
Newsgroups: net.micro
Title: Re: Re 8086: Good thing come in
Article-I.D.: sri-arpa.1149
Posted: Fri Apr 29 12:38:00 1983
Received: Mon May  2 03:06:47 1983


			  "The s/370 operates most of the time in a world
    of 12 bit addressing -- all that will fit into the 12 bit displacement
    field."

This is somewhat misleading.  Since every memory reference instruction can
designate a base register plus the 12-bit offset, with some instructions
having provisions for a separate index register as well, and since it is
standard practice to use several base registers pointing to consecutive
memory areas, programs are in practice not limited to a 12-bit address space.
That is, it is not necessary to break up a program larger than 4k bytes into
subroutines in order to make use of multiple base registers; the assembler
knows to use the right one, assuming you tell it that you're setting them up.
Fortunately, nobody designs new machines like this any more.