Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!cbmvax!grr From: grr@cbmvax.cbm.UUCP (George Robbins) Newsgroups: comp.sys.amiga Subject: Re: Help: definitions and terminology Message-ID: <1699@cbmvax.cbmvax.cbm.UUCP> Date: Tue, 21-Apr-87 02:22:56 EST Article-I.D.: cbmvax.1699 Posted: Tue Apr 21 02:22:56 1987 Date-Received: Wed, 22-Apr-87 02:15:24 EST References: Reply-To: grr@cbmvax.UUCP (George Robbins) Organization: Commodore Technology, West Chester, PA Lines: 162 Somewhat against my better judgement I'm going to answer these, although I know others have already attempted the feat... In article cb29#@andrew.cmu.edu (Chad Kavanaugh Bisk) writes: > >I have been listening to much of the discusion about various graphics >abilities and distinctions of the Amiga vs. the IBM PS/2 (anyone know what >the PS/1 was?) There was nothing called a PS/1 - I guess PS/2 is just saying this is the second generation - PC/XT/AT being the first. >Amy vid chip Confusion - Amy is a diminutive used in some circles to refer to an Amiga. The Amiga functions are actually distributed over 3 custom chips, but it appears as only entitity from the programming model point of view. >video gate array This (VGA) refers to a "all-in-one" custom chip used in the PS/2 machines to handle video output. >blitter >copper These are subfunction "processors" in the Amiga custom chips. The blitter (aka bimmer) performs bit-oriented logical operations on bit planes. "blit" is an formalism/algorithm for performing such operations. The copper is another "processor" that runs in synchronism with the beam position on the CRT screen. While it's organization is simple, it allows tricky screen manipulations without visual artifacts and with minimal 68000 overhead. >chipmem >fastmem Loosely (!!!) chip memory is that memory that the custom chips are able to access directly. Expansion memory is accessable by the processor and external DMA, but not the custom chips. Although the chip memory is normally shared by the 68000 and the display without interference, some video modes and all blitter/copper actions may co-opt processor cycles. Fast memory is memory that is not affected by the custom chip cycle "sharing". That is a program running in fast memory can run full speed even though you may be beating the chip memory to death. Internal expansion (> 512K) on new machines is somewhere in between in that it works like chip memory, but isn't accessable by the current custom chips. External memory is still "fast". >color look-up table >color registers Means of translating a limited number of bits per pixel to one of a many color shades. >X (or X Windows) >SunNews X or the X Window System is a windowing system created out of Project Athena at MIT. NeWS (New Window System) is a windowing system created by Sun Microsystems. They are contending for the "standard" window system on workstations. Both require Berkeley style unix. >Agnus, fat agnus, paula, portia, diane[sic], etc. These are the Amiga custom chips. Agnus - Address Generator - Contains all the pointer registers, update logic and DMA control. Also the blitter, copper, sprite engines, etc, and sync generation. Fat Agnus - is a modified Agnus chip used in the A500. It integrates various logic from the A1000 board into the Agnus package, but does not add any new capabilities. Paula (orginally Portia) handles most of the random I/O functions includingserial port, floppy and sound. Denise (orginally Daphne) handles the video shifting, color lookup table, sprite/bitplane priority andmouse motion. Two 8520 "Versatile I/O" chips handle the mundane I/O operations including the keyboard, parallel port, floppy control and RS232 control. >SUPER_BITMAP A bitmap bigger than can actually be displayed on the screen. >What is bandwidth (I need a really exact definition of this one, it's all >kind of fuzzy in my head, must not be enough bandwidth, eh?), and how does it >relate to graphics display? Bandwidth is basically the number of bits per unit time that you can get through a device. In the case of video, it is the number of bits/second you need to handle screen refresh. In the case of high resolution/lots of bits/pixel displays this becomes a critical design factor. The Amiga performs 1 16-bit memory cycle every ~280 nanoseconds. This yields a total bandwidth of 7.16 Megabytes/Second. Normally half of these cycles are used by video refresh and half by the processor, however it is possible to select video modes that use more than 3.58 Megabytes/Second, in which case cycles normally allocated to the processor will be used. This is a basic design limitation of the Amiga chipset and can only be avoided by implementing faster memory cycles, specialized memory chips, 32-bit wide video memory, external display hardware or some combination of the above. The Atari ST suffers from the same limitations, but doesn't have any display modes fancy enough to exceed half the available bandwidth. >Other related terms of interest: >CLIPPER >AM29000 The Clipper (Fairchild), AM29000 (AMD) and MIPS chip (MIPS) are ground up "super-micro" processor chips intended for the workstation market. None of them have had much effect on the microcomputer market yet. They encompass various speed/cost of implementation tradeoffs. The 68020/68030 and 386 chips are high-end versions of existing micro-processor families that are also targetted at the workstation market. Since they have some compatibility with the chips currently being used in micro, they are more likely to show up in the next generation of systems. >TurboAmiga CSA's 68020 Expansion box for the A1000. >the AT&T blitter beast AT&T has some interesting videodisplay boards/systems. Not clear what effect these will have on the general purpose micro market. >other blitters (how about a knowledgeable comparison?) Atari has some kind of blit chip in the works, but seems to have trouble getting chips into systems and on the shelf. TI has a very powerful video processor chip that will show up on a number of PC/AT compatible video cards. It might show up on some A2000 expansion cards eventually... There are a number of other blit chips or video/processor chips incorporating "blit" functions. There is nothing really magical about the Amiga blitter. It just was the first to provide blit functions at a reasonable cost and integrate the blit functions with all the other system functions. -- 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)