From: utzoo!decvax!harpo!seismo!rlgvax!guy
Newsgroups: net.micro
Title: Re: Re: What is a 16032?
Article-I.D.: rlgvax.1099
Posted: Fri Feb 25 01:09:16 1983
Received: Fri Feb 25 07:33:14 1983

The rumor I heard about the 16032 is that it was originally intended to
*be* a VAX-11 lookalike, but that National Semi had just gotten sued by
DEC for making a PDP-11 lookalike (and lost) and decided against it.
Yes, it is quite like a VAX, Semitic bit/byte/word order and all.
8 32-bit general registers, plus the PC, static base (see below),
(stack) frame pointer, stack pointers (user and kernel mode).  It has
VAX-like addressing modes, with either the 8 GPRs or the PC, Static Base,
Frame Pointer, or Stack Pointer used as a pointer register.  No auto-increment
or decrement though.  Also, it has *four* indexed modes (a la VAX); for
some reason, the operand size is encoded in the index mode rather than being
taken from the instruction.  The addressing modes are less "regular" than
the VAX, and seem more tailored to the use algorithmic languages would have
for them.

The instructions are the standard collection of two-operand highly-orthogonal
instructions that any general register machine *should* have.  No CRC16
and the like, and no full packed decimal.  It has the extract/insert bit
field instructions, and index checking/stepping instructions (like VAX-11
"index").  It has a similarly orthogonal set of instructions for the
floating point coprocessor (IEEE standard single- and double-precision),
and a set of instructions reserved for a "custom" coprocessor.

The MMU is a standard demand-paged MMU (24-bit virtual address in,
25-bit physical address out) with 512-byte pages.  The page table is itself
paged.  Furthermore, in a very un-VAX-like step, the page table has
*REFERENCE BITS*!  It has a large set of registers for program debugging;
it can remember the addresses the last two branch/jump/call instructions
came from, and can support two breakpoints - the break can occur on a read,
a write, or an execute from that location.

The data sheets that I am reading this from were handed out at UNICOM by
National Semi.  The chips are the NS16032 CPU, 16082 MMU, and 16081 FPU.

					Guy Harris
					RLG Corporation
					...!decvax!mcnc!rlgvax!guy