Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site amiga.amiga.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!whuxl!whuxlm!akgua!gatech!ut-sally!pyramid!amiga!rj From: rj@amiga.UUCP (Robert J. Mical) Newsgroups: net.micro.amiga,net.micro.atari Subject: Re: Reply to: Questions about ST vs. AMIGA Message-ID: <425@amiga.amiga.UUCP> Date: Fri, 20-Dec-85 15:45:02 EST Article-I.D.: amiga.425 Posted: Fri Dec 20 15:45:02 1985 Date-Received: Sun, 22-Dec-85 00:11:57 EST References: <342@unmg.UUCP> <840@h-sc1.UUCP> <352@well.UUCP> <382@pedsgd.UUCP> Reply-To: rj@wizard.UUCP (Robert J. Mical) Distribution: net Organization: Commodore-Amiga Inc., 983 University Ave #D, Los Gatos CA 95030 Lines: 26 Xref: watmath net.micro.amiga:1230 net.micro.atari:2060 Summary: Amiga interleaves its bus access In article <382@pedsgd.UUCP> bobh@pedsgd.UUCP (Bob Halloran) writes: >Granted, the graphics chips relieve the 68000 from dealing with the >display, as it must in the Mac, but the 68000 and the various co-processors >must still contend for access to memory. YES, I/O can proceed independently, >etc., but only ONE of the processors can use memory at a time. This >HAS to impact the throughput of the 68000. This is true. But don't forget that the Amiga interleaves its access to the bus, using every available cycle, even the odd ones, whenever possible. All of the DMA, including the display processors, use the odd cycles. This enormously cuts down the contention for the bus. The result of this is that the 68000 and other co-processors get to run at full speed regardless of display processing. Only when the display gets elaborate -- 640 across (either interlaced or not) and 4 bit-planes (16 colors onscreen) -- is there a significant lag in CPU performance. The same goes for the other DMA devices: sprite, disk, and audio. With a simple display, a few sprites and some simple tones playing, you can fill a disk buffer and still have truly minimal interference with the performance of the 68000. --------------------- - Greetings - - =Robert J. Mical= - - Commodore-Amiga - ---------------------