Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!usc!elroy.jpl.nasa.gov!decwrl!mcnc!ncsuvx!news From: kdarling@hobbes.ncsu.edu (Kevin Darling) Newsgroups: comp.sys.amiga.introduction Subject: Re: Beginer Questions (How Does the amiga use MEMORY?) Message-ID: <1991Jan10.220945.8464@ncsuvx.ncsu.edu> Date: 10 Jan 91 22:09:45 GMT References: <6812@crash.cts.com> <1991Jan10.131436.248@zorch.SF-Bay.ORG> Sender: news@ncsuvx.ncsu.edu (USENET News System) Organization: NCSU Computing Center Lines: 29 LK> However, when the blitter is in use, or the LK> coprocessor (COPPER), you see some of this cycle stealing. As a LK> result, the CPU can usually run quite close to full speed on the LK> CHIP RAM bus, but there is almost always some activity which slows LK> it down a bit. And of course any heavy graphics use will cause LK> considerable slowing if the CPU is forced to run code out of the LK> CHIP RAM area. And displaying hires gfx. A while back I got curious, because the Amiga hardware manual seems to infer that the higher res modes (over four bitplanes in lores 320 or two bitplanes in hires 640) could block out the cpu/blitter entirely. So I did some calculations and came up with these figures, which weren't near as bad as I had thought: XY Res Colors Lockout amt ------- ------ ----------- 320x200 32 14% 360x480 32 18% ( % of cycles that 320x200 Ham 27% the cpu and blitter 360x480 Ham 36% are locked out of 640x200 8 27% video RAM access) 640x200 16 54% 720x480 8 36% 720x480 16 73% 736x480 16 75% I believe them to be correct... but add salt if you wish. ;-) kevin PS: belated thanks to Kent for the new groups!