>While this is true of Quadra built-in video, which tops out at 1152x870 >(except for the 630 & the like, which top out at 832x624), I was recently >looking at AppleSpec, & they say that some early PCI PowerMacs (namely the >4400, 7/8200) that can have as little as 1 meg of VRAM can't do 1280x1024, >but those upgraded to 2 or more can. > >Not sure why. Maybe something to do with bandwidth?
The Video picture displayed on the screen is made of pixels. In order to display these the graphics processor (GPU) requires enough RAM to remember every colour value and what order to put them on screen (i.e. vertical size, horizontal size, bit depth, etc.) On a screen with 1-bit (eg. SE/30) screen graphics at 512x384 size, requires 196,608 bits of memory, one bit for each pixel, which is 24k. The same size screen at 8-bit colour (say a Macintosh LC) requires 8 times that amount of RAM, 192K. That accounts for colour depth related to RAM. Take our screen of 1-bit 512x384 graphics and times both dimensions by 2 and you get 1024x768. as each side doubles the screen size increases by a factor of 4x the pixels, so 1024x768 at 1-bit requires 4 times as much RAM, 96k. Now take a video card with 1MB vRAM. Because the video card does not allot all RAM for the screen matrix, it has to remember the other stuff too,it can not physically remember an 1152x870 at 8-bit as it requires 979k and is too big for the allotted size of memory space. Apple also abandoned 1-bit and 4-bit colour depth successively so most PowerMacs do a minimum of 8-bit colour as it was all that was acceptable (most later programs and games required it). You'll be delighted to know Apple are trying to do away with 8-bit in OS X but it is still available in 10.1. Anyhow, the fact a 1MB PowerMac can't do 1152x870 is that the VRAM is not big enough to remember all the pixels and their locations on screen and other stuff. So there you go. That's how it works folks :). -- -- Mark Benson Any spelling errors are attributed to PEBKAC Vintage Macs List Nanny SilValleyPirate - AIM silicon_valley_pirate_uk - Yahoo! Visit Flat Pack Macs Online: <http://fpm.gotdns.com> Macintosh LC Central -- Quadlist is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Enter To Win A | -- Canon PowerShot Digital Cameras start at $299 | Free iBook! | Support Low End Mac <http://lowendmac.com/lists/support.html> Quadlist info: <http://lowendmac.com/lists/quadlist.shtml> The FAQ: <http://macfaq.org/> Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/quadlist%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
