Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!ll-xn!mit-eddie!uw-beaver!cornell!batcomputer!itsgw!imagine!pawl8.pawl.rpi.edu!jesup From: jesup@pawl8.pawl.rpi.edu (Randell E. Jesup) Newsgroups: comp.sys.amiga Subject: Re: Instant Windows (making the copper/blitter obsolete) Message-ID: <603@imagine.PAWL.RPI.EDU> Date: 2 Apr 88 21:10:02 GMT References: <2007@pasteur.Berkeley.Edu> Sender: news@imagine.PAWL.RPI.EDU Reply-To: beowulf!lunge!jesup@steinmetz.UUCP Organization: RPI Public Access Workstation Lab - Troy, NY Lines: 69 In article <2007@pasteur.Berkeley.Edu> c162-fe@zooey.Berkeley.EDU (Jonathan Dubman) writes: >A little while back (in the Mac II vs. Amiga article) I mentioned that I had >an idea that would make the blitter obsolete. Well, here it is. >The principle is so simple that I am sure it has been thought of before: >EVERY WINDOW IS A HUGE SPRITE. The graphics chip can handle multiple >overlapping rectangular regions with differing priorities and (maybe) palette. >In essence, it is more like the copper than the blitter. To move a window, >merely change the x and y positions. The chip could handle off-screen movement >and clipping very easily. To move a window to the front, merely shuffle the >priorities. No refreshing. No software clipping. Can you say, >"blindingly fast"? Yes, it has been thought of before; and yes, there are chips that do things like this. The problem is that you are going to be limited in the number of these on screen at a time. The memory bandwidth problems will impose limitations, and the circuitry to decide priorities. If you want transparency, you must fetch the bitmaps for EVERY window in their entirety, THEN decide how to handle overlaps. Sprites work because they are small. The fetching is done early on the line, and 8 sprites is a small enough number that the priority stuff is fairly simple. The proper way to think of it is that there are about 800 pixels by 4 bitplanes worth of memory bandwidth per horizontal line. To do windows as sprites, including transparency, it would limit you to about 4 windows in monochrome. You can have more if they aren't on the same horizontal line, or aren't full width, but that really gets to be a pain (look at the problems dealing with Vsprites). >Low >memory bandwidth, incredible performance by today's standards. And the >windowing idea is not going away. You get higher bandwidth if you worry >about transparency, which i would insist upon, but parallel processing can >lower the bandwidth with very little overhead. And each of the processors >is extremely simple- I'm talking equivalent of a dozen counters and latches, >etc. Naturally, there will have to be some finite limit to the "see-through", >like 8 deep or something. The ONLY way you could get your transparency is to have seperate memory spaces for each "window processor", and that would be very complicated/ expensive. The performance would be nice, but the limitations wouldn't be. Look how people are annoyed by GEM only allowing (4? 8?) windows open at a time. It also would be much more expensive if you either want more windows, or colors. >Have you ever used a Mac II? The window motion is SOOOOO SLOW. It is very >annoying to use. The slowness of the graphics and the inability to distinguish >conceptual contexts (can't have different programs on different screens- you >just get everything running on one cluttered screen that each application >probably completely fills) are the major reasons preventing me from getting >one. (Oh, and also the price.) Notice how much faster the Amiga is at graphics due to the blitter? Remember that the amiga is using a 16-bit bus, at 7Mhz, and an old technology chip (the blitter). Think about the posibility of a 32-bit blitter, running at 14Mhz (or better), with new (faster) technology, and if you really want all-out performance, use a blitter per bitplane. >OK- I'm ready for the bad news. Somebody respond and tell me that Fairchild >or Texas Instruments or somebody has had the GFX1152 for three years that >already does everythig I'm saying. I know they exist, don't remember who makes them. // Randell Jesup Lunge Software Development // Dedicated Amiga Programmer 13 Frear Ave, Troy, NY 12180 \\// beowulf!lunge!jesup@steinmetz.UUCP (518) 272-2942 \/ (uunet!steinmetz!beowulf!lunge!jesup) BIX: rjesup (-: The Few, The Proud, The Architects of the RPM40 40MIPS CMOS Micro :-)