🚀 go-pugleaf

You need a certain number of bytes free in the framebuffer to do
Z-buffering on a Voodoo2. When you're in 1024x768 resolution the memory
requirements for a double buffered display (essential for games) & Z
buffering are as follows:

Memory needed for display (16-bit colour depth):
(1024x768x16x2)/8 = 3,145,728 bytes (the 2 is for double buffering)
= 3MB

Memory needed for Z (16-bit Z on a V2):
(1024x768x16)/8 = 1,572,864 bytes
= 1.5MB

3+1.5 = 4.5 > 4MB therefore no Z buffer can be used.

Andrew

Oh yeah, you'll also find that a 12MB V2 still suffers from the same
limitation. The extra 4MB on that card is for textures only.

Andrew

Maple Moose <maple-moose@home.com> wrote in message
news:OKeN3.2098$AX.75933@news1.rdc1.ab.home.com...
> I once ran across the calculation but had since forgotten it.  Could some
> one enlight me the math as to why V2 8MB or 12MB can
> only do 800X600 16 bit with Z buffer but could do
> 1024X768 16 bit without Z buffer?  I know about the 4MB frame buffer
> limit but couldn't get the math right.  Thanks.

You need to include an extra frame, for double-buffering (page-flipping).

800x600 x2 (bytes per pixel) x3 (2 image buffer and 1 Z-buffer) = 2.88 MB.

1024x768x2x3 = 4.7MB - too big to fit in 4MB.

Actually, at 800x600 there is enough room for triple-buffering:

800x600x2x4 = 3.84 MB.

--
Mike Smith

There are perhaps 5% of the population that simply *can't* think.
There are another 5% who *can*, and *do*.
The remaining 90% *can* think, but *don't*.
-- R. A. Heinlein

Well then, what about SLI mode, using 2 V2's?

REM

On Thu, 14 Oct 1999 09:22:16 +0100, Andrew Hodgson
<ahodgson@nortelnetworks.com> wrote:

>You need a certain number of bytes free in the framebuffer to do
>Z-buffering on a Voodoo2. When you're in 1024x768 resolution the memory
>requirements for a double buffered display (essential for games) & Z
>buffering are as follows:
>
>Memory needed for display (16-bit colour depth):
>(1024x768x16x2)/8 = 3,145,728 bytes (the 2 is for double buffering)
>= 3MB
>
>Memory needed for Z (16-bit Z on a V2):
>(1024x768x16)/8 = 1,572,864 bytes
>= 1.5MB
>
>3+1.5 = 4.5 > 4MB therefore no Z buffer can be used.
>
>Andrew

>Well then, what about SLI mode, using 2 V2's?

That allows you 1024x768

I've seen the math calculation some programer did and it comes up a liitle
short in the proper allocation of memory per processor.
mjdart

Klingon da Prevert! wrote in message <380e85f8.685313@news.mciworld.com>...
>Well then, what about SLI mode, using 2 V2's?
>
>REM
>
>On Thu, 14 Oct 1999 09:22:16 +0100, Andrew Hodgson
><ahodgson@nortelnetworks.com> wrote:
>
>>You need a certain number of bytes free in the framebuffer to do
>>Z-buffering on a Voodoo2. When you're in 1024x768 resolution the memory
>>requirements for a double buffered display (essential for games) & Z
>>buffering are as follows:
>>
>>Memory needed for display (16-bit colour depth):
>>(1024x768x16x2)/8 = 3,145,728 bytes (the 2 is for double buffering)
>>= 3MB
>>
>>Memory needed for Z (16-bit Z on a V2):
>>(1024x768x16)/8 = 1,572,864 bytes
>>= 1.5MB
>>
>>3+1.5 = 4.5 > 4MB therefore no Z buffer can be used.
>>
>>Andrew
>

I had a fwe games running in 1024x768 on my monster 3d 2 12 meg with diamond
drivers. I heard tehre are soem drivers (blackmagic?) that will elt you do
1024x768 on all v2's that work with it.

--
If it aint broke, I'll fix it anyway.