Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!decwrl!amdcad!lll-crg!caip!daemon From: Felton.PA@Xerox.COM@caip.RUTGERS.EDU Newsgroups: net.micro.amiga Subject: Re: interlace mode Message-ID: <1096@caip.RUTGERS.EDU> Date: Mon, 27-Jan-86 20:47:26 EST Article-I.D.: caip.1096 Posted: Mon Jan 27 20:47:26 1986 Date-Received: Thu, 30-Jan-86 01:34:12 EST Sender: daemon@caip.RUTGERS.EDU Organization: Rutgers Univ., New Brunswick, N.J. Lines: 39 From: Felton.PA@Xerox.COM > The limitation is the number of > bytes you're shoving through the graphics hardware every frame, and I > would believe that med-res mode on the Atari cuts the number of colors > displayable in half? Twice the resolution = half the colors = same number > of bytes/line. The above is incorrect. One of the things I have always liked about changing word sizes is the fact that as you add digits linearly your range of representable values grows geometericly. If you add one bit to a three bit word you get a net gain of eight combinations (8 combinations for a three bit word and 16 combinations for a four bit word). But, If you add one bit to a four bit word you get a net gain of 16 combinations (16 combinations for a four bit word and 32 combinations for a five bit word). The same effect is true for screen memory. Each bit plane added to the screen memory doubles the number of colors that may be display. This is true regardless of what percentage of the total screen memory that one bit plane makes up. Resolution, on the other hand, does not work this way. Inorder to double the resolution (display twice the number of pixels on the screen) one must double the screen memory (not just add another bit plane, as with doubling the number of colors). In order to double the screen resolution the size of the bit planes must be doubled. In order to maintain the same display bandwidth (same screen memory size) this results in the need to cut the number of bit planes in half. With the example sighted above doubling the resolution required reducing the number of bit planes from 4 to 2. Lossing 2 bit planes means cutting you color selection to 1/4 of its original size. Thus, the atari ST displays 16 colors in low resolution color mode and 4 colors in high resolution color mode. John p.s. Sorry if this simple minded discussion of bit planes bored you. As for my self, I find it fascanating.