Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!columbia!rutgers!caip!cbmvax!daveh From: daveh@cbmvax.cbm.UUCP (Dave Haynie) Newsgroups: net.micro.apple Subject: Re: Re: InCider's comments on the new //GS Message-ID: <812@cbmvax.cbmvax.cbm.UUCP> Date: Mon, 29-Sep-86 15:18:35 EDT Article-I.D.: cbmvax.812 Posted: Mon Sep 29 15:18:35 1986 Date-Received: Wed, 1-Oct-86 01:24:16 EDT References: <285@neoucom.UUCP> Organization: Commodore Technology, West Chester, PA Lines: 39 > One thing positive that I can say is that the 65816 is a pretty > neat CPU. I'd like to get my hands on a //GS to dhrystone it. > From what I've read, the claims are that the 3 MHz65816 can beat an 8 > MHz 68K chip. Also WDC promised a 65832 that fits the same socket > by 1987. > > Bill Mayhew Don't count on it. A 2.8MHz 65C816 can, in many cases, beat a 4.77MHz 8088. But not a 68000 at 8MHz. While the 65C816 at 2.8MHz does run a slightly faster bus speed than the 68000 at 8MHz, it has several major problems with using this speed: (1) The bus is still 8 bits wide, the 68000 bus is 16 bits wide. The 68000 is going to clobber the '816 when 16 bit operations are required. (2) The 65C816 still only has one general purpose register, the 68000 has 16 reasonably general registers, each of which is twice the width of the '816's register. Register based computation is much, much faster than memory based computation; this is one of the major principles of RISC architectures (not to imply that either machine is RISC, neither is). (3) The 68000 has a much more powerful instruction set. Just the multiply instruction alone is a big win in any numeric computations. (4) The '816 is a bit awkward/inefficient to program, especially considering the instruction overloads. Every instruction can operate on either 8 or 16 bit data, based upon a bit set in the status register. This makes switching between byte and word oriented data clumsy. (5) An upgrade to a 32 bit processor, in a pin-compatible package, won't gain you very much. A large part of the advantage of a 32 bit processor over a 16 bitter, or a 16 over an 8, is the doubling of the data bus. A pin compatible replacement would take a minimum of 4 times as long to run each 32 bit instruction based in memory as the equivalent processor with a 32 bit data bus. Also, WDC promised to have the 65C816 chip ready about 4 years ago, and its just now avilable in production quantities, from GTE. So I wouldn't be waiting on the edge of my seat for a 32 bit version. -- ============================================================================ Dave Haynie {caip,ihnp4,allegra,seismo}!cbmvax!daveh These opinions are my own, though if you try them out, and decide that you really like them, a small donation would be appreciated.