Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!cbmvax!grr From: grr@cbmvax.UUCP Newsgroups: comp.sys.amiga Subject: Re: 6502 Vs 68000, lets get it straight . Message-ID: <1531@cbmvax.cbmvax.cbm.UUCP> Date: Wed, 11-Mar-87 02:39:13 EST Article-I.D.: cbmvax.1531 Posted: Wed Mar 11 02:39:13 1987 Date-Received: Wed, 11-Mar-87 21:47:53 EST References: <8703100226.AA07627@ingres.Berkeley.EDU> Reply-To: grr@cbmvax.UUCP (George Robbins) Organization: Commodore Technology, West Chester, PA Lines: 40 In article <8703100226.AA07627@ingres.Berkeley.EDU> hatcher@INGRES.BERKELEY.EDU (Doug Merritt) writes: >Matt Dillon wants to straighten us all out on how much faster a 68000 >is than a 6502. What he says seems to be good information, but it misses >the entire point that George Robbins (and I and others) are trying to make. > >The point is not how fast you can do things on one versus the other. >That is different than doing an emulation. I think we can agree that a 8 MHz 68000 is n:n>4 times faster than a 1 MHz 6502 on generic code segments where the bigger register store and 16 bit instructions pay off. Howver for the fairly simple task that map nicely into 6502 instructions - byte moves, indexing 256 byte tables, etc. the 68000 may only be n:n<2 times faster. NOW! What sort of operations are you going to be doing in your interpreter? You will have to do exactly those dinky little things where you have the least performance advantage over the 6502. Also you have interpretive overhead to deal with, although hopefully the power of the 68000 helps here. To strike the final blows, remember the the C64 has memory mapped I/O! This means for *every* memory access (possibly including reads, even I-fetches) you have to test for side effects! Sound bad? Next since since the C64 has dynamically switchable ROM/RAM overlays, you get to add either a layer of indirection or other mapping function. Oh, pain! Count all those nice little 68000 cycles you're eating. Hmmm, anything else? Remember C64 games typically synchronize little code fragments to raster positions and change VIC registers on the fly. So of course you're interleaving this VIC emulation somehow... Anybody got some 32 MHz 68030's? If you had told the 6502 designers that the 6502 would be one of the most popular *general purpose* microprocessors ever, they would have laughed. It was a variation on the Motorola 6800 theme (which was more general purpose) with an instruction set to give tight, fast code and and external interface to allow optimal use as a micro-controller chip. You know, traffic lites, blenders, microwaves and that sort of thing... -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)