Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!mit-eddie!uw-beaver!ubc-vision!van-bc!nvanbc!lawrenc From: lawrenc@nvanbc.UUCP (Lawrence Harris) Newsgroups: comp.arch,comp.sys.nsc.32k,comp.sys.intel,comp.sys.m68k Subject: Re: Question: on-chip or off-chip MMU? Message-ID: <391@nvanbc.UUCP> Date: Sat, 25-Apr-87 22:00:31 EDT Article-I.D.: nvanbc.391 Posted: Sat Apr 25 22:00:31 1987 Date-Received: Tue, 28-Apr-87 00:39:46 EDT References: <5635@shemp.UCLA.EDU> <122@motsj1.UUCP> Reply-To: lawrenc@nvanbc.UUCP (Lawrence Harris) Followup-To: junk Organization: L.H. Computing Lines: 60 Summary: Flame on motorola propaganda campains Xref: mnetor comp.arch:1106 comp.sys.nsc.32k:119 comp.sys.intel:205 comp.sys.m68k:415 **** FLAME ON **** In article <122@motsj1.UUCP> rich@motsj1.UUCP (Rich Goss) writes: >In article <5635@shemp.UCLA.EDU> fan@CS.UCLA.EDU (Roy Fan) writes: >>-------------- <> The above is all OK but, the rest of this appears to be pure propaganda which I have the feeling is normal policy for motorola as most of the advertizing seems to run down competitors products by quoting misleading information such as what follows. Besides this is the ncs 32k group and not a place to advertize motorla cpu's. I was involved in a project using the Zilog Z8000 processor a few years back and recieved literature from motorola at that time makeing fantastic claims for their chip and virtually lieing about the limitations of the Z8000 (just for example they claimed the Z8000 could only address 64k bytes when in fact it was 8meg not including split I/D possiblities). >One should look at the potential for a particular MMU scheme being >incorporated in future generation of processors. You should look >at the 286 MMU and the 386 MMU. They are not compatible. The MMU >in the 68030 is compatible with the 68851 PMMU chip. > As far as I am aware (without doing much research) it is a subset, not a superset (ie. downward compatable). Further the Compaq 386 runs XENIX 286 from the box so how uncompatable can the 386 MMU be? Agreed it has more features than the 286 but you don't have to recode applications before you can use the 386! >As to whether an MMU should be on chip with the CPU depends on >the application. The 68030 is an excellent choice for work >staions and systems which support multitasking and/or multiuser >operating systems. The 68020 is a good choice for the above >when coupled with the 68851 PMMU or the users own MMU. Also the >68020 is an excellent choice for embedded controller applications Some more edited out here. > >-- Rich Goss >Motorola Western Regional Field Applications Engineer for 68000 >Family The Z8000 was a fantastic chip for embedded controller applications capable of handling the interupt rate from a floppy disc controller for example without DMA support. I guess the fact that he works for motorola gives him an interest in promoting motorola's products, but I do get tired of how far they stretch the truth sometimes. ps. The above should not be taken to indicate a preference for any of motorola or intel products. I actually prefer the national cpus myself (but use both intel and motorola). -- ------------------------------------------------------------------------------ UUCP: tectronix!uw-beaver!ubc-vision!van-bc!nvanbc!lawrence SNAIL: 733 Sylvan Ave., North Vancouver, B.C., Canada, V7R 2E8 PHONE: 1-604-736-9241 (09:00-17:00 PDT)