gjw@floyd.UUCP (Greg Wroclawski) (12/15/83)
I have a hard time beleiving that the tandy 2000 graphics capabilities are as stated in several articles on the net. Full 8 color resolution at 640x400 pixels would require 3 bits of memory for each pixel. 640x400x3=768000 bits of bit mapped display memory. Dividing by 8 shows that 96000 bytes of memory are required. I would believe that full 8 color graphics has far less resolution than the 640x400. Note that the IBM PC 's highest resolution 640x200 graphics mode is only two color(foreground and background). This only requires 128000 bits or 16000 bytes of bit mapped display memory. The only way simultaneous use of 8 colors is possible at the tandy's resolution is if bit mapped character display blocks are used ala TI's 9918 Video Display Controller. This limits the specification of colors of adjacent pixels.
jpm@bnl.UUCP (John McNamee) (12/17/83)
Yes, the Tandy 2000 really does do 8 colors with 640 x 400 pixel resolution. From what I have been able to tell from using the GW-Basic that comes with the 200, itsseems they really do use 3 bits per pixel. The local repair shop only got schematics for the text card and the base unit, but the tech said full info should be available in January. Another article said that they used a 188 chip. This is not true. The 2000 uses a real 186 chip with 16 bit data paths. John McNamee ..!decvax!philabs!sbcs!bnl!jpm jpm@BNL.Arpa
riber@uicsl.UUCP (12/17/83)
#R:floyd:-203000:uicsl:7000037:000:391 uicsl!riber Dec 16 14:04:00 1983 BELIEVE IT !!!!!!!!!!!!!!! I saw one in the store yesterday. Very, Very impressive. You have a choice of 8 (yes a full 8) colors to display from a 16 color palatte. How they do it is not explained in thier advertisement, but believe me, it does it.Real neat. BUT GO SEE ONE. It's about time we were offered some decent color graphics at a decent price. pur-ee!uiucdcs!uicsl!riber
dmmartindale@watrose.UUCP (Dave Martindale) (12/18/83)
8 colours from a palette of 16? Can you individually select which of the 16 colours the 8 possible pixel values map to? Something is funny here. If the video is separate RGB (and it would have to be to get 640 pixels/line) and they used only 1-bit DACs (each of RGB is either off or full on) you get only 8 possible colours. 2-bit DACs give you 4 levels of intensity for each of RGB, and a total of 64 possible colours. If they already have more than 8 colours (implying the presence of at least one DAC with more than 1 bit of input) and they have the ability to map the 8 pixel values individually to one of a larger number of palette colours (implying a colour lookup table) it is a real shame that they simply didn't use three 2-bit DACs and a 6-bit lookup table, giving a palette of 64 colours. Going to 3-bit DACs would have allowed 8 distinct intensity levels of grey (or any colour), allowing you to do reasonable antialiased lines and characters, increasing the apparent resolution of the display. The antialiasing could be done using any colour of lines on any colour background (though you could only choose one foreground and background colour for the whole screen), and the total palette would increase to 512 colours. All of this without increasing the image memory at all, just improving the video output hardware a bit. Anyone know what they really did, and why they didn't go just a bit further? I would guess that the additional hardware in the video output would be cheap compared to the display memory. Dave Martindale than 640x480