mfriedel@slate.mines.colorado.edu (Friedel Michael) (04/24/91)
Sorry for those of you who have seen most of this already, but a lot of people are asking the same kind of questions again, and they are wasting a lot more bandwitdht and my nerves. 1) Speed of Display ( my opinion) The display is faster than a '30 cube. Depending on the number of open windows and their respective bit-levels. (Yes it makes a difference). As most applications come up in gray-scale (2bit) by default the display is almost as fast as monochrome 0'40, meaning that the difference is barely noticeable. Yes it is possible to make the display dog-slow, but only if the the windowsizes exceed the available RAM (and the swapper gets more than its fair share), and that takes BIG windows and a lot of them. But this is true for all color displays. So as usual more memory helps. (20 is a reasonable value,32 is a lot better). 2) Number of available colors 4096 colors can be displayed at once on the screen out of a set of 16million. John Graves from NeXT wrote to me: >Each pixel on NeXTstation Color is represented by 16 bits in DRAM, four bits >each for red, green, and blue, plus four bits of "alpha" for transparency. In >VRAM (video ram), each pixel is represented by12 bits, four each for red, >green, and blue. Overlaping images are "composited" by the PostScript window >manager, taking account of their transparency, before they are put into VRAM. >Try dragging around an icon for a WriteNow document or use Molecule.App (if you>have an extended system) to see the effects of transparency. >The RAMDAC receives four bits from the VRAMs for each color (red, green, and >blue). These four bits address a color palette RAM inside the RAMDAC, >selecting an eight bit DAC value. The color palette is set by the window ^^^^^^^^^^^^^^^ >manager (PostScript) based on the brightness control and a gamma correction >function to get the best set of sixteen intensities from the available 256 for ^^^^^^^^^^^^^^^^ >each channel of red, green, and blue. The gamma function is used to compensate >for the non-linearity of the phosphors in the monitor. The color palette is >not accessible to the user, to prevent one application from messing us the >color palette for all applications. Translation: There are 4096 colors of a set of 16.7 million available, meaning that 256 shades of gray are posssible. 4) Developing color apps No, you don't need a color station, or a NeXtdimension to develop color apps. The windowmanger renders the Postscript output to the available bitlevels of the screen. 6) Memory The ColorStation does not use the same chips as the other slabs. It needs 80ns 72 pin SIMMS. (1 or 4meg, single sided only). Memory is added o in banks of two. On a 12meg slab it has two 4Meg and four 1Meg installed leaving 2 slots empty. It also has another slot to add extra memory for the DSP chip. (one 64pin socket). Hope this helps Michael Friedel (mfriedel@basalt.Mines.Colorado.EDU) -- /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ No user serviceable part inside. Warranty void if opened modified or tampered with. No batteries included. *
madler@nntp-server.caltech.edu (Mark Adler) (04/25/91)
In article <1991Apr24.122116.25517@slate.mines.colorado.edu> mfriedel@slate.mines.colorado.edu (Friedel Michael) writes: >>The RAMDAC receives four bits from the VRAMs for each color (red, green, and >>blue). These four bits address a color palette RAM inside the RAMDAC, >>selecting an eight bit DAC value. The color palette is set by the window > ^^^^^^^^^^^^^^^ >meaning that 256 shades of gray are posssible. Doesn't sound that way to me. I interpret what John Graves had to say as there being three look up tables, each with a four bit address and an eight bit output. Thus, at any one time, you are still limited to sixteen shades of true gray. To be able to display 256 shades of gray, you would need a 4Kx24 ram in the RAMDAC, which it doesn't sound like it has. Mark Adler madler@pooh.caltech.edu