daveb@amiga.UUCP (Dave Berezowski) (01/18/86)
<eat my line> There has been a lot of talk (and flak) about the apparent 'unusable' interlace mode of the AMIGA. I have seen a 640 x 400 screen that didn't seem to flicker at all and looked dynamite! BUT the programmer did use a trick to accomplish this feat. The trick is to plot a pixel ON and ABOVE the line where the pixel is to be placed. This still results in an effective resolution of 400 lines BUT reduces the flicker to almost zilch. I saw this implemented on a terminal program and a graphics display and they both looked great on a 1080 monitor. Give it a try, the results may surprize you! Regards, David Berezowski (CBM/AMIGA East Coast)
breuel@h-sc1.UUCP (thomas breuel) (01/18/86)
| There has been a lot of talk (and flak) about the apparent |'unusable' interlace mode of the AMIGA. I have seen a 640 x 400 |screen that didn't seem to flicker at all and looked dynamite! |BUT the programmer did use a trick to accomplish this feat. | | The trick is to plot a pixel ON and ABOVE the line where the |pixel is to be placed. This still results in an effective resolution |of 400 lines BUT reduces the flicker to almost zilch. I saw this |implemented on a terminal program and a graphics display and they |both looked great on a 1080 monitor. Give it a try, the results |may surprize you! | | Regards, David Berezowski (CBM/AMIGA East Coast) Sure, if you use 640x400 as a 640x200 mode, then you won't see any flicker, you won't have any higher resolution either, though, and you'll waste a lot of memory. The only thing I don't like about the AMIGA (apart from its price) is the fact that it doesn't manage to produce 640x400 graphics. I have seen several demos in high-resolution mode, and the flicker is really unbearable for any real work. WHAT I WOULD LIKE TO KNOW IS: is Commodore/AMIGA planning on releasing a version of the AMIGA in which this problem has been fixed (e.g. in which the monitor can be run at either 60Hz or 70Hz)? Is there a hardware patch that can be applied to current machines to solve the problem? I find that for serious use as a desktop workstation, a resolution of 640x200 pixels is just not enough. The Mac is just barely usable (slightly lower horizontal resolution and larger vertical resolution), and the LISA is probably the only low-end work-station on which you can afford to have two reasonably sized windows open at the same time. Thomas.
farren@well.UUCP (Mike Farren) (01/19/86)
In article <877@h-sc1.UUCP>, breuel@h-sc1.UUCP (thomas breuel) writes: > | The trick is to plot a pixel ON and ABOVE the line where the > |pixel is to be placed. This still results in an effective resolution > |of 400 lines BUT reduces the flicker to almost zilch. I saw this > > Sure, if you use 640x400 as a 640x200 mode, then you won't see > any flicker, you won't have any higher resolution either, though, > and you'll waste a lot of memory. This isnt 640X200 mode. You still have 400 (399, actually) vertical pixel locations, it's just that each pixel is now 2 lines high instead of one. It's the same sort of thing that a lot of machines (specifically Atari 800 and Apple II) did to avoid horizontal color aliasing when using a standard NTSC type composite monitor. > WHAT I WOULD LIKE TO KNOW IS: is Commodore/AMIGA planning on > releasing a version of the AMIGA in which this problem has > been fixed (e.g. in which the monitor can be run at either > 60Hz or 70Hz)? Is there a hardware patch that can be applied > to current machines to solve the problem? The necessary fix would be fairly expensive. The biggest reason for the 640 X 200 limitation on each field is to reduce the bandwidth requirements of the coprocessor and the memory, and to allow the CPU more cycles. Maintaining the current hardware capabilities and adding the extra capability you describe isn't an easy job. (Before I hear anything about the Atari ST and its 640X400, 70Hz screen, let me remind you that that is a one-bit-per- pixel monochrome screen. It's ONLY color option is 320X200. If you are willing to accept THAT limitation, then the problem isn't too hard. If you want a color screen such as the Amiga's, at a reasonable cost, compromises have to be made.) -- Mike Farren uucp: {your favorite backbone site}!hplabs!well!farren Fido: Sci-Fido, Fidonode 125/84, (415)655-0667
breuel@h-sc1.UUCP (thomas breuel) (01/20/86)
||| The trick is to plot a pixel ON and ABOVE the line where the |||pixel is to be placed. This still results in an effective resolution |||of 400 lines BUT reduces the flicker to almost zilch. I saw this || ||Sure, if you use 640x400 as a 640x200 mode, then you won't see ||any flicker, you won't have any higher resolution either, though, ||and you'll waste a lot of memory. | | This isnt 640X200 mode. You still have 400 (399, actually) vertical |pixel locations, it's just that each pixel is now 2 lines high instead of |one. It's the same sort of thing that a lot of machines (specifically |Atari 800 and Apple II) did to avoid horizontal color aliasing when using |a standard NTSC type composite monitor. This may do the trick for certain kinds of graphics. For a high-resolution text display, it may make your characters look nicer, but it does not allow you to display significantly more characters on the screen. | The necessary fix would be fairly expensive. The biggest reason for the |640 X 200 limitation on each field is to reduce the bandwidth requirements |of the coprocessor and the memory, and to allow the CPU more cycles. |Maintaining the current hardware capabilities and adding the extra capability |you describe isn't an easy job. (Before I hear anything about the Atari ST |and its 640X400, 70Hz screen, let me remind you that that is a one-bit-per- |pixel monochrome screen. It's ONLY color option is 320X200. If you are |willing to accept THAT limitation, then the problem isn't too hard. If you |want a color screen such as the Amiga's, at a reasonable cost, compromises |have to be made.) Yes, that is precisely the point. For word processing and program development I vastly prefer high monochrome resolution to low colour resolution. That is not a bad limitation, it is a reasonable compromise (between cost and performance). What counts for those applications is whether you can display one, two, or four usable windows on the screen at the same time, not whether your menu bar is green and your pop-up menus are pink. I guess we just have different applications in mind. For my purposes, a machine with true 640x400 monochrome resolution is just superior to one with 640x200 colour resolution because I can display more text on the screen at the same time. Since I otherwise like the AMIGA, I really regret that it doesn't have this capability. It is unfortunate to hear that Commodore/AMIGA seems to have no intention of adding a high-resolution monochrome mode. Thomas.
long@sask.UUCP (Warren Long) (01/21/86)
> <eat my line> > > There has been a lot of talk (and flak) about the apparent > 'unusable' interlace mode of the AMIGA. I have seen a 640 x 400 > screen that didn't seem to flicker at all and looked dynamite! > BUT the programmer did use a trick to accomplish this feat. > > The trick is to plot a pixel ON and ABOVE the line where the > pixel is to be placed. This still results in an effective resolution > of 400 lines BUT reduces the flicker to almost zilch. I saw this > implemented on a terminal program and a graphics display and they > both looked great on a 1080 monitor. Give it a try, the results > may surprize you! > > Regards, David Berezowski (CBM/AMIGA East Coast) Doesn't this little trick drop the resolution down to 200 lines???? (at least for all intents and purposes.) Warren Long University of Saskatchewan Canada
mykes@3comvax.UUCP (Mike Schwartz) (01/21/86)
There is little doubt in my mind that the Amiga could have had much better resolution than it already does, but the tradeoff would have been non-NTSC standard. This means that not only could the Amiga not be plugged into a TV and features like GENLOCK would be much more expensive. A distinct advantage of being NTSC standard is that not only can input from a video camera be mixed in, but the output can be recorded on standard video tape. Blame for the flicker in interlace mode should be placed on the NTSC standard, not the Amiga. NTSC is not exactly the best quality video standard anyway.
mjg@ecsvax.UUCP (01/21/86)
> > > The trick is to plot a pixel ON and ABOVE the line where the > pixel is to be placed. This still results in an effective resolution > of 400 lines BUT reduces the flicker to almost zilch. I saw this > implemented on a terminal program and a graphics display and they > both looked great on a 1080 monitor. Give it a try, the results > may surprize you! > > Regards, David Berezowski (CBM/AMIGA East Coast) Doesn't this mean that the vertical positioning resolution is 400 lines but that objects can only be described to the nearest 1/200th of the screen height. Mike Gingell ..decvax!mcnc!ecsvax!mjg
tynor@gitpyr.UUCP (Steve Tynor) (01/22/86)
>you describe isn't an easy job. (Before I hear anything about the Atari ST >and its 640X400, 70Hz screen, let me remind you that that is a one-bit-per- >pixel monochrome screen. It's ONLY color option is 320X200. If you are >willing to accept THAT limitation, then the problem isn't too hard. If you >want a color screen such as the Amiga's, at a reasonable cost, compromises >have to be made.) Medium res (high res color) on the atari st is 640x200.
tainter@ihlpg.UUCP (Tainter) (01/22/86)
> you describe isn't an easy job. (Before I hear anything about the Atari ST > and its 640X400, 70Hz screen, let me remind you that that is a one-bit-per- > pixel monochrome screen. It's ONLY color option is 320X200. If you are > Mike Farren WRONG! The ST also has 640x200 color, albeit with fewer color choices. --johnathan a. tainter
rb@ccivax (01/23/86)
> In article <877@h-sc1.UUCP>, breuel@h-sc1.UUCP (thomas breuel) writes: > The necessary fix would be fairly expensive. The biggest reason for the > 640 X 200 limitation on each field is to reduce the bandwidth requirements > of the coprocessor and the memory, and to allow the CPU more cycles. > (Before I hear anything about the Atari ST > and its 640X400, 70Hz screen, let me remind you that that is a one-bit-per- > pixel monochrome screen. It's ONLY color option is 320X200. Minor Correction: you also get colors (4) in 640X200 mode on the ST! > If you are > willing to accept THAT limitation, then the problem isn't too hard. If you > want a color screen such as the Amiga's, at a reasonable cost, compromises > have to be made.) So how about this as an option (to get the best of both worlds!)! Add 640X400 monochrome at 70HZ interlaced. This would be ideal for editing text and large draftings that end up getting sent to a 'monochrome' copier for quick and cheap duplication (the majority of office documents). Then use the multicolor interlaced mode for stuff that will be sent to the print shop for color printing. From what I've seen in the Amiga Specs, it seems to have more than enough bandwidth for this (mono 70HZ) mode and still have about the same CPU bandwidth as it would in the 640X200X4 at 60HZ mode. It might even be a simple software change. There are still a lot of situations where all you need is easy to read black and white (like stuff for copiers). Also, there is no reason why you couldn't get 80x50 lines on the screen by using the same 'fonts' you would normally use on the 640X200 screen (not to mention being able to look at two documents at once). Of course, if the 'monochrome' could be put on a color display, you could still pick your choice of forground and background colors from the color registers (White on Black background is hard to do on any color monitor).
mykes@3comvax.UUCP (Mike Schwartz) (01/23/86)
The double height pixel trick for interlace mode yields 399 vertical positions that the top pixel (of the two) can be. However, the OS does not take advantage of this trick, but a Mac-write style word processor could.
farren@well.UUCP (Mike Farren) (01/23/86)
I wrote: >>you describe isn't an easy job. (Before I hear anything about the Atari ST >>and its 640X400, 70Hz screen, let me remind you that that is a one-bit-per- >>pixel monochrome screen. It's ONLY color option is 320X200. If you are >>willing to accept THAT limitation, then the problem isn't too hard. If you >>want a color screen such as the Amiga's, at a reasonable cost, compromises >>have to be made.) And Steve Tynor replied: > Medium res (high res color) on the atari st is 640x200. Thanks for the information. I hadn't realized there was a med-res mode. It still doesn't change things, though. 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. It might be possible, by limiting the bit-planes to one (or possibly 2), to get the bandwidth you'd need to put out a 640X400 non-interlaced screen, as someone else suggested. The secondary problem that that brings up is simple: you need a different monitor. A monitor that will handle 640X400 is forced to operate with a MUCH higher horizontal frequency, and would either be much more expensive (if color), or incompatible with the lower resolution modes (rendering a lot of software incompatible), or both. I'm pretty sure this is the reason the STs have two non-intermixable monitors. -- Mike Farren uucp: {your favorite backbone site}!hplabs!well!farren Fido: Sci-Fido, Fidonode 125/84, (415)655-0667
dca@edison.UUCP (01/24/86)
> In article <877@h-sc1.UUCP>, breuel@h-sc1.UUCP (thomas breuel) writes: > > | The trick is to plot a pixel ON and ABOVE the line where the > > |pixel is to be placed. This still results in an effective resolution > > |of 400 lines BUT reduces the flicker to almost zilch. I saw this > > > > Sure, if you use 640x400 as a 640x200 mode, then you won't see > > any flicker, you won't have any higher resolution either, though, > > and you'll waste a lot of memory. > > This isnt 640X200 mode. You still have 400 (399, actually) vertical > pixel locations, it's just that each pixel is now 2 lines high instead of > one. It's the same sort of thing that a lot of machines (specifically > Atari 800 and Apple II) did to avoid horizontal color aliasing when using > a standard NTSC type composite monitor. > Huh? obviously I am missing something here. It seems to me that by making each pixel 2 lines high we have just created a screen that will hold only 640x200(virtual) pixels. I would imagine that the 640x200 essentially does exactly this, i.e. expands that pixel height. Therefore it seems to me that using the 640x400 strictly in this manner is equivalent to using the 640x200 mode except more memory (and cycle stealing) is utilized. The advantage I might see to this method is that the screen could use 640x200 equivalent mode for all parts of the screen for which it is unecessary to have maximum resolution and thus minimize the flicker. David Albrecht
gnu@hoptoad.uucp (John Gilmore) (01/25/86)
In article <511@well.UUCP>, farren@well.UUCP (Mike Farren) writes: > In article <877@h-sc1.UUCP>, breuel@h-sc1.UUCP (thomas breuel) writes: > > WHAT I WOULD LIKE TO KNOW IS: is Commodore/AMIGA planning on > > releasing a version of the AMIGA in which this problem has > > been fixed (e.g. in which the monitor can be run at either > > 60Hz or 70Hz)? Is there a hardware patch that can be applied > > to current machines to solve the problem? > > The necessary fix would be fairly expensive. The biggest reason for the > 640 X 200 limitation on each field is to reduce the bandwidth requirements... There is a technical fix for video memory bandwidth problems, called "video rams". These are ordinary dynamic RAM chips which also have a second access port which scans out a row of 512 bits serially based on an input clock. While this scanning goes on, there is NO interference with the normal memory access. Once per 512 bits, you must do a special memory cycle to load a different row of bits into the shifter. This gives the CPU something like 99.8% access and the video 100% access. For example, each row might be a line of a 512-wide screen. If you need N bit planes, you use N chips. (These are 256Kx1 RAMs anyway, so you will have at least 16 of them in a 68K-based system). This does place some constraints on how video memory is allocated but they can be lived with. While video rams are more expensive than normal DRAMS, in a system with the price of an Amiga, the added features (large # of bitplanes in the display with no performance degradation) easily outweigh the cost difference. Of course, these can not be retrofitted into an existing design like the Amiga; they need to be designed in from scratch. A lot of designers are skeptical about video rams, as I was, until I saw them used to halve the access time of a frame buffer and reduce its cost too. -- # I resisted cluttering my mail with signatures for years, but the mail relay # situation has gotten to where people can't reach me without it. Dammit! # John Gilmore {sun,ptsfa,lll-crg,nsc}!hoptoad!gnu jgilmore@lll-crg.arpa
farren@well.UUCP (Mike Farren) (01/26/86)
In article <633@edison.UUCP>, dca@edison.UUCP writes: > Huh? obviously I am missing something here. It seems to me that by making > each pixel 2 lines high we have just created a screen that will hold only > 640x200(virtual) pixels. I would imagine that the 640x200 essentially does (The discussion was about plotting 2-high pixels in the 640X200 mode) No, you don't have 640 X 200 virtual pixels. You have 640 X 399 screen locations which can hold a pixel, which pixel is two lines high. For example: Screen lines --> X......... Note the pixels are composed of two dots (what X..X...... are normally called pixels), and that adjacent ...X..X... pixels can overlap by one line. This means ......X... that the ONLY structures on the screen which will lose resolution are those which are made up of only one vertical dot. I would like to see someone construct a high-res font which uses this principle - I think it would look GREAT! -- Mike Farren uucp: {your favorite backbone site}!hplabs!well!farren Fido: Sci-Fido, Fidonode 125/84, (415)655-0667
preece@ccvaxa.UUCP (01/27/86)
> Huh? obviously I am missing something here. It seems to me that by > making each pixel 2 lines high we have just created a screen that will > hold only 640x200(virtual) pixels. /* Written 8:27 am Jan 24, 1986 > by dca@edison.UUCP in ccvaxa:net.micro.amiga */ ---------- You have a little of each. There are 399 possible pixel locations, since the upper half of the double-height pixel can be on any line except the bottom line. But, the screen is only 200 pixels high. What you do about overlapping pixels has not been described in anything I've seen here -- I suppose the later plotted pixel would overwrite the earlier. You could probably use this trick, with cleverly designed fonts, to get 25x80 characters that were better than the standard IBM color adapter but not as good as a Mac. This might be a reasonable compromise. On the other hand, if I were designing a text oriented program for a machine I knew to have 400 lines of vertical resolution, I would want to use more than 25 lines of text, sacrificing some text quality for quantity. The main problem with current text screens, on personal computers or terminals, is that you can't get enough on them to make windowing really useful. The tall pixel idea really doesn't do anything to make the Amiga better suited for answering that problem. -- scott preece gould/csd - urbana uucp: ihnp4!uiucdcs!ccvaxa!preece arpa: preece@gswd-vms
breuel@h-sc1.UUCP (thomas breuel) (01/28/86)
||Huh? obviously I am missing something here. It seems to me that by making ||each pixel 2 lines high we have just created a screen that will hold only ||640x200(virtual) pixels. I would imagine that the 640x200 essentially does | | (The discussion was about plotting 2-high pixels in the 640X200 mode) | No, you don't have 640 X 200 virtual pixels. You have 640 X 399 screen |locations which can hold a pixel, which pixel is two lines high. For example: | |Screen lines --> X......... Note the pixels are composed of two dots (what | X..X...... are normally called pixels), and that adjacent | ...X..X... pixels can overlap by one line. This means | ......X... that the ONLY structures on the screen which | will lose resolution are those which are |made up of only one vertical dot. I would like to see someone construct |a high-res font which uses this principle - I think it would look GREAT! It may look GREAT, but it will not solve the problem I posed originally: you won't be able to get twice as many characters vertically in the interlaced mode. To get lots of information on the screen, you NEED 640x400 without any constraints or tricks, and without any flicker. Thomas.
Felton.PA@Xerox.COM@caip.RUTGERS.EDU (01/28/86)
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.
mykes@3comvax.UUCP (Mike Schwartz) (01/28/86)
In 640 x 400 mode, plotting pixels 2-tall yields 399 vertical positions. Consider the following illustration: line1 | x line2 | x x line3 | x x line4 | x This illustrates positioning 3 2-tall pixels at different vertical positions. In order for there to be only 200 vertical positions, the pixels would be plotted like this: line1 | x line2 | x line3 | x line4 | x line5 | x line6 | x In other words, in interlaced mode, plot the pixel at the point you would normally plot, plus the point below (or above) it.
cem@intelca.UUCP (Chuck McManis) (01/29/86)
> ... > some discussion about bits vs combinations etc > ... > > 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. You will note John that a common 'double' the resolution interpretation is to double *both* X and Y resolutions. This actually displays 4 times the number of pixels on the screen. Now in the case of the Atari and the Amiga they 'double' the resolution from 320 X 200 by only doubling the X direction to 640. This does not help a lot of graphics applications that would really like reasonably square pixels. The Amiga will display 640 X 400 (bringing it much closer to the 3:2 aspect ratio (or is it 4:3?) of the 'standard' CRT, to a lot of people this is the only interpretation of the term when applied to raster displays. Interestingly, the Amiga still displays 16 colors/pixel because it also cuts the bandwidth requirements in half. --Chuck -- - - - D I S C L A I M E R - - - {ihnp4,fortune}!dual\ All opinions expressed herein are my {qantel,idi}-> !intelca!cem own and not those of my employer, my {ucbvax,hao}!hplabs/ friends, or my avocado plant. :-}
farren@well.UUCP (Mike Farren) (01/29/86)
In article <889@h-sc1.UUCP>, breuel@h-sc1.UUCP writes: [ after a discussion of using two-high pixels in 640X400 mode] > It may look GREAT, but it will not solve the problem I posed originally: > you won't be able to get twice as many characters vertically in the > interlaced mode. To get lots of information on the screen, you NEED > 640x400 without any constraints or tricks, and without any flicker. Yes it will. Example (two versions of a slash): ........ ......X. ......X. One high pixels .....XX. Two high pixels. .....X.. | ....XX.. (Note - only ONE pixel ....X... <---- ...XX... height difference!) ...X.... ..XX.... ..X..... .XX..... .X...... XX...... X....... X....... In short, there is NOTHING that says that the two-high pixels must start on an even line. The only thing you have to do is to ensure that no pixel "stands alone". -- Mike Farren uucp: {your favorite backbone site}!hplabs!well!farren Fido: Sci-Fido, Fidonode 125/84, (415)655-0667
ewhac@well.UUCP (Leo L. Schwab) (02/06/86)
x.UUCP> Sender: Reply-To: ewhac@well.UUCP (Leo L. Schwab) Followup-To: Distribution: Organization: Whole Earth Lectronic Link, Sausalito CA Keywords: [ gulp! ] As a new poster to this newsgroup, I'm getting somewhat puzzled by all this "discussion" on why interlace mode on the Amiga does/doesn't suck rocks. Why don't you all just face it: We all have different eyes and perceive flicker (or lack thereof) to different degrees. Yes, 640 x 400 on the Amiga flickers, but depending on who you are, you may not care. Personally, I say, "ICK!" to myself when I first turn on interlace mode, but then after a few minutes, my eyes glaze over and I hardly notice it. This is just me though. J. Random User may not think so (and by the discussion going on here, it's obvious that everybody doesn't agree). Personally, I like to think of 640 x 400 as being reserved for "CAD only" type applications. You know, the kind of application that absolutely requires the highest resolution available. People also seem to complain about the character set being just this side of unreadable. Again, this is subjective, and when it becomes possible to change the system font, it will become a moot point. Why don't we all just agree to differ on this point and move on to more interesting things (like the Boing Wars :-)? Leo L. Schwab well!ewhac dual!unicom!schwab