Newsgroups: comp.arch
Path: utzoo!utgpu!watserv1!watdragon!rose!ccplumb
From: ccplumb@rose.uwaterloo.ca (Colin Plumb)
Subject: Re: R4000
Message-ID: <1991Feb1.223326.18683@watdragon.waterloo.edu>
Sender: daemon@watdragon.waterloo.edu (Owner of Many System Processes)
Organization: University of Waterloo
References: <45448@mips.mips.COM>
Date: Fri, 1 Feb 91 22:33:26 GMT
Lines: 45

I absolutely loathe reading press releases, so for those of you too
lazy to go to comp.sys.mips, here's the capsule summary.

- Expected to be available later this year.

- Will be available, in pin-comaptible versions, from IDT, LSI Logic,
  NEC, Performance Semiconductor, and Siemens.

- Talk of a range of performances, with references to faster versions but
  not slower ones.

- Runs existing binaries.

- Single chip.

- 64-bit integer ALU, 64-bit FP ALU, 8K I-cache, 8K D-cache, MMU,
  primary and secondary cache control on-chip.  It is not clear to me
  if the primary cache being controlled is the on-board one, or they
  control two levels of off-chip cache.

- 64-bit addresses as well as data.  John Mashey has been talking about
  the address space crunch for a few years now, so this isn't a huge
  surprise, but it's still interesting.

- "Superpipelined", issuing two instructions per cycle.  I don't understand
  this, as they distinguish it from the usual superscalar implmentation
  (i960CA, RS6000) so I quote from the press release:

> Superpipelining overlaps the execution of multiple instructions, so
> that while the first step of an instruction is performed, the second
> step of the previous instruction is also executed.

> Both the integer and floating point units are superpipelined.
> Superpipelining requires less circuitry than other multiple-instruction
> issue techniques, so it leaves room on the chip for other functions.
> Further, it provides greater integer processing than most other
> techniques, whose benefits are confined mainly to floating-point
> operations.  Superpipelining, therefore, is particularly important in
> commercial applications, where balanced integer and floating-point
> performance are desirable.

- "Foundation" multiprocessing support hardware.  No useful details.
  Lots of talk about flexibility.
-- 
	-Colin
