Hi all,

due to the fact that English is not my mother tongue language, I’m not sure I really understand the thread.

>From my point of view, there is two different “aspects” (points of view) here:

• Hardware (Macintosh) colors capabilities, (the Macintosh can or cannot be VRAM upgradable)
• Software (NetBSD) colors capabilities.



For the former (Hardware), you can compute the possible available colors using the formulae (if my memory is still right):
Screen.Width * Screen.Height * Color.Bit.Depth

Example for a Quadra 700:
-------------------------

Monitor size: 640 * 480
Number of pixels: 640 * 480 = 307,200
So you need a minimum of 37,5 KB of VRAM to get Black and White video
(307,200 / 8) / 1,024 = 37,5

If you want 8 bits video (256 colors)
(307,200 / 8) * 8 / 1,024 = 300 
You need a minimum of 300 KB of VRAM to get 256 colors video


If you want 16 bits video (256 colors)
(307,200 / 8) * 16 / 1,024 = 600 
You need a minimum of 600 KB of VRAM to get 256 colors video


If you want 32 bits video (256 colors)
(307,200 / 8) * 32 / 1,024 = 1,200 
You need a minimum of 1,200 KB of VRAM to get > 16,000,000 colors video

Of course, if your monitor is larger, you need more and more video RAM.

Still in the Quadra 700, you can upgrade the video RAM up to 2 MB.

If you connect a 16" Color Display Apple monitor to the very same Quadra 700 with 2 MB of VRAM, you will be able to see a maximum of
“Thousand Colors”...

Number of pixels: 832 * 624 = 1,038,336
(1,038,336 / 8) * 16 / 1,024 = 2,028

So it is possible to see 32767 different colors in this 16" (in fact 15 bits colors !).


That was the Hardware part. Now the software part.

The only thing I can say about software is that it is possible to show more colors but not on the whole screen. You’re in the dark ?
Yes, I try to explain differently...

On your 8 bits screen, you can use a small part of it to display a 16 bits image ... using 16 bits to display the image. BUT, the
other part of the screen must use less bit depth. I think I saw QuickTime doing that (but I’m not sure).
Also, I do not have any idea on how this is possible (as a programmer’s point of view), but “on the paper” it is doable: use the
same amount of VRAM (globally), but the VRAM buffer is not used as a 8 bit buffer, but instead a variable bit depth VRAM buffer. I
hope this time it is more clear (not sure...)
Just like if you use a 1 bit offscreen graphic to display an image and plot another - but 16 bits and smaller - offscreen graphic to
display another image at 16 bits colors and send all of this to the VRAM buffer.


I stop here because I was beyond my actual knowledge (but I think this is doable),

Emile

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