BARRETT%FOREST.ECIL.IASTATE.EDU@cunyvm.cuny.edu (Marc Barrett) (04/11/90)
Many people are saying that they wish there were more constructive
questions around here. Well, here is a constructive question to get
one started...
does anyone know whether or not the A2360 ("Lowell") video card
has the ability to accomplish such things as palette-switching
(on-the-fly between scanlines) or HAM modes? I was told be someone
(probably not here, though) that this card can emulate (in software)
the current Amiga chipset.
If this card can do this, this may be Commodore's way out of the
fix that they've found themselves in with the now-far-superior video
capabilities of the Apple 8/24GC video card. If the A2360 can
accomplish a normal 320x200 6-bitplane HAM mode, then it should
also be able to accomplish a 1024x768 8-bitplane "Extended HAM" mode
(262,144 colors at once!). If the card can switch palettes between
scanlines (A LA Dynamic HiRes) then it could display approx. 200,000
colors at once (256 colors per line * 768 lines). If it can do
both, Apple would be in deep trouble!
However, there are a LOT of 'IF's here. I hope it has these
capabilities, but I haven't heard anything about it being able
to do so. If it doesn't, then I renew my call for Commodore to
bring out some serious video hardware, because it is needed.
-MB-steveg@umd5.umd.edu (Steve Green) (04/11/90)
In article <16450@snow-white.udel.EDU> BARRETT%FOREST.ECIL.IASTATE.EDU@cunyvm.cuny.edu (Marc Barrett) writes: >[...] > If this card can do this, this may be Commodore's way out of the >fix that they've found themselves in with the now-far-superior video >capabilities of the Apple 8/24GC video card. If the A2360 can >accomplish a normal 320x200 6-bitplane HAM mode, then it should >also be able to accomplish a 1024x768 8-bitplane "Extended HAM" mode >(262,144 colors at once!). If the card can switch palettes between >scanlines (A LA Dynamic HiRes) then it could display approx. 200,000 >colors at once (256 colors per line * 768 lines). If it can do >both, Apple would be in deep trouble! >[...] Actually, with the standard Apple monitor and 8/24 card, you would be limited to 307,200 colors at one out of as pallette out of the 16.8 million. (One color per pixel). With a 1024x768x8 card for the Mac, the number is boosted up to 786,432 colors at once. 200,000 colors would not affect Apple sales 1 BIT. :-) -- What do these names have in common? Bob, Flo, Augie, Curtis, Gordon, Rick, Rhonda, Meep, Bismark, Skip. ...did I miss any?? steveg@umd5.umd.edu
mcmahan@netcom.UUCP (Dave Mc Mahan) (04/11/90)
In article <16450@snow-white.udel.EDU> BARRETT%FOREST.ECIL.IASTATE.EDU@cunyvm.cuny.edu (Marc Barrett) writes: > > does anyone know whether or not the A2360 ("Lowell") video card >has the ability to accomplish such things as palette-switching >(on-the-fly between scanlines) or HAM modes? > > If this card can do this, this may be Commodore's way out of the >fix that they've found themselves in with the now-far-superior video >capabilities of the Apple 8/24GC video card. If the A2360 can >accomplish a normal 320x200 6-bitplane HAM mode, then it should >also be able to accomplish a 1024x768 8-bitplane "Extended HAM" mode >(262,144 colors at once!). If the card can switch palettes between >scanlines (A LA Dynamic HiRes) then it could display approx. 200,000 >colors at once (256 colors per line * 768 lines). If it can do >both, Apple would be in deep trouble! > > -MB- Well, let's look at your numbers. If we assume that we get 30 screen refreshes per second, and that the processor changes all 256 colors EVERY scan line, and that it takes 1/2 microsecond for each color on the 2360 or whatever processor your using (which I doubt it can do, but maybe), we find that : Time_per_scan = 1/30 seconds = 33,333 uSecs Time_taken_to_switch_1_line = 256 colors * 768 * .5 uSec = 98,304 uSecs Total_%_of_CPU_Time = 98,304 uSec/33,333 uSec * 100% = 29.5% Are you willing to sacrifice a conservative 29.5% of your available CPU resources to obtain this type of resolution? I'm not. Please not that this estimate is VERY conservative, and is probably somewhere closer to 50% or 60% by the time the CPU gets finished figuring out which palette it should use, where to get it from, etc. Now you have the power of the 68030, running at a little more than the throughput found in the 68000 you have in the standard A500, A1000, and A2000. Seems like kind of a shame, don't you think? And we haven't even taken into account all the extra memory required to store all those palettes. This figure comes out to around 576 Kbytes, just to store the palettes for each line. That's approximately 64 Kbytes more than are in my current amiga, but just barely doable in a machine with a fat agnus. The data for this wonderful picture you are creating will take up about 768 Kbytes. Add that to what we have already consumed for our color palette, and we come up with just about 1.3 Mbytes to store one picture. Slightly more than 30% bigger than the current fat agnus can deal with. And we haven't even taken into account contention on the chip bus or the extra memory required to store links to the color palette so we can switch at such high rates. As we can see, sometimes C= DOES know what they are doing by including custom chips in the amiga to do this kind of processing. Now we know why they invented custom chips, don't we? -dave