Actually the PowerPCs (& Quadras) with 1 MB VRAM can indeed do 1152x870 at 8
bits; it's 1280x1024 that you get only when you up it to 2 (on the
PowerPPCs) -- according to AppleSpec. Of course, they've been wrong
before....
But your excellent summary of the mathematics of resolution & bit-depth
would seem to explain why: Power Mac internal video can't do 4-bit depth or
less, & you need 2 megs (when they come in 1-meg units) to achieve the
buffer for 8-bit pixels (1,280k).
I suggested bandwidth lack (moving the pixels fast enough) because that is
the explaination given me for why these same PPCs can't do 1152x870 at
24-bit (even when they have the VRAM to hold all the pixels), & also (to get
back on topic, or at least on the right list) why the Quadra/LC/Performa 630
& the machines modeled after it can't do 16-bit at 832x624, even though they
have 1 meg of (in this case) DRAM specially dedicated to video.
I wonder why Apple decided to cut the bottom off for PPCs at 8 bits? To
simplify the OS?
~~
On Sun, 26 May 2002 09:23:22 +0100
Mark Benson <[EMAIL PROTECTED]> wrote:
>
>>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.)
[...] 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
>
[...]
--
Over,
Jutso
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