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On Sun, 5 Oct 1997, Steve Parker wrote: > On Sun, 5 Oct 1997, Harald Milz wrote: > > > The tech specs are on > > http://www.us.pc.ibm.com/products/thinkpad/5aea_11da.html > > The max color depth still doesn't seem to mean much. The table lists.. > > Display & Resolution > E: 12.1" SVGA TFT - 256K colors @ 800x600 > 11.3" SVGA DSTN - 64K colors @ 800x600 > Other models: 11.3" SVGA DSTN - 256 colors @ 800x600 > 12.1" SVGA TFT - 64K colors @ 800 x 600 > > Since 256 color VGA is actually 256 colors out of a palette of 256K > colors I highly doubt the panel is only good for 256 colors. Which 256 Here's the deal, LCDs have their own drivers, their own chipset, their own memory, etc. This is independent of the video chipset in your laptop and it's memory and such. DSTNs (and I'm pretty sure TFTs) can only display 3 colors - bright red, bright blue, and bright green. For an DSTN or TFT to display a other intensity colors, it has to flick the pixel on and off at a certain frequency (not sure of TFT, but this is the case for DSTN). The ratio of on to off determines how much light gets through and thus how bright the color is. The *total* number of displayable colors is determined primarily by the design of the LCD (how fast can a pixel be flipped on and off). The number of *simultaneously* displayable colors is determined by the chipset that drives the LCD. The LCD's (not the computer's) chipset drives this on/off behavior. Depending on the chipset and memory, certain color combinations are possible just like with your video chipsets. 256 colors from a palette of 256k, 32k fixed colors, 64k fixed colors, 16M fixed colors, and even oddball ones like 256 colors from a palette of 4096, or 4096 fixed colors. A palette is used for the same reason it's used in video cards - there isn't enough memory to code every possible color, but the monitor (LCD) is capable of displaying them so not using them would be a waste. A palette lets you code just certain colors (using less memory), but allows them to use the full range of the monitor's (LCD's) capability. So when using a monitor, the video chipset draws the display in memory, then converts it to an analog signal which goes to the monitor. When using an LCD, the video chipset draws the display in memory, and I'm pretty sure it passes that info digitally to the LCD chipset, which translates it into on/off sequences for the LCD, and these signals go to the LCD which does its thing and creates the illusion of different colors. So what this chart probably means is: > E: 12.1" SVGA TFT - 256K colors @ 800x600 This TFT can show 256k distinct colors simultaneously > 11.3" SVGA DSTN - 64K colors @ 800x600 This DSTN can only show 64k colors simultaneously. > Other models: 11.3" SVGA DSTN - 256 colors @ 800x600 This DSTN can show only 256 colors simultaneously, probably from a palette of 4096, 16k, 32k, or 64k colors. Nearly everything nowadays can do better than a 4096 palette. It probably cannot do 32k simultaneous or it would've been advertised as such. The reason is a limitation in the memory or chipset of the LCD itself (just like certain video cards don't have enough memory or don't have a RAMDAC that let's them do 32k colors). > 12.1" SVGA TFT - 64K colors @ 800 x 600 This DSTN can show 64k colors simultaneously. Things become somewhat tricky if you can switch resolutions because the color depth/palette available can change just like with video cards. The final PC manufacturer rarely specifies all these different available modes, but if you can track down the manufacturer of the LCD, they can usually tell you exactly what the screen is capable of. The problem is that the same model of computer often uses different types of LCDs (we know the 701 uses at least 2), and the performance can vary substantially. So to answer the final question, no that particular DSTN probably cannot do better than 256 simultaneous colors. But since the video chipset of the 560 series is the same throughout, you should be able to do 64k on an external monitor. But there's one other caveat. 800x600x16bit = 960000 bytes. I believe the 560 only has 1MB of VRAM = 1048576 bytes. That leaves just 88576 bytes for video acceleration functions (bit blts, redrawing uncovered windows, etc.). You can run it at 64k, but it's going to be a *lot* slower than the 2x performance hit you'd expect going from 8bit color to 16bit color. Phew. -- John H. Kim kim@mak.com