Path: utzoo!attcan!uunet!peregrine!elroy!ames!lll-tis!oodis01!uplherc!esunix!jsnow From: jsnow@esunix.UUCP (John Snow) Newsgroups: comp.sys.apple Subject: Re: 65816 v. 680x0 Message-ID: <1086@esunix.UUCP> Date: 16 Nov 88 03:30:29 GMT References: <871@dogie.edu> Distribution: na Organization: Evans & Sutherland, Salt Lake City, Utah Lines: 32 From article <871@dogie.edu>, by terranova@vms.macc.wisc.edu (John Terranova): > BTW: I have heard that the 65816 has a very efficient instruction set > (highly piplined, perhaps?) and would run rings around a 68000 running > at the same clock speed. Can anyone verify or deny this for me? Just > wondering. Well, let's just say that the 6502 family in general do more per clock cycle than do most other microprocessors. For this reason, the clock speed HAS to be lower because the chip needs more time between clock cycles to do everything that it is doing. Yes, if the 65816 ran at the same clock speed as a 68000, the 65816 would vastly outperform the 68000. It would also require faster and more expensive memory chips to keep up with it since it would access the RAM in one half of a clock cycle whereas the 68000 would use 3 clock cycles for its memory cycle. Actually, the 2.8 MHz 65816 in a GS compares very well with the 7.8 MHz 68000 running in a Mac. Despite the fact that it must do twice as many memory accesses to get 16-bits of information, the 65816 can execute many instructions at the same overall speed as the Mac's 68000. I sat down one day and calculated several of them and was surprised to find that many were within about 5% of the 68000's speed. The place that really slows the GS down is when it has to access slow RAM, meaning the graphics really suffer a penalty due to the graphics RAM being slow RAM. Hopefully, a future GS will remove the slow RAM from the system. -- ----------------------------------------------------------------------------- John F. Snow UUCP:{ucbvax,decvax}!decwrl!esunix!jsnow Evans & Sutherland Computer Corp. Compuserve: 71550,1152 BIX: johnfsnow Salt Lake City, Utah "Apple ][ forever!"