🚀 go-pugleaf

Sebastian Kaliszewski <Sebastian.Kaliszewski@softax.com.pl> wrote in message
news:81giki$sce$1@euler.softax.local...
> Freon wrote in message <383b326d.0@news.mocc.net>...
> >I dont think you understand the operation.  Each chip renders it's own
> >lines on the screen.
> >To do that, the textures have to be duplicated in the RAM for each chip.
> >By using half as much RAM, you would leave too little for textures.
> >Using 32MB of DDR would get the same bandwidth, but not the same amount
of
> >texture RAM.
> >
>
> It would be only slightly less.

Slightly less?  How about doing a little math.
64/2 = 32.
32/2 = 16.
Pretty simple.

> The main point is that textures should not
> be duplicated for two chips if the chips were sharing DDR RAM instead of
> using separate memory sets.

They cant work that way.  If it could be done, it would have been done
before even Voodoo2 was released.
Each chip has to work from it's own set of textures.  Besides, if they
shared the same memory for the textures, you would now have multiple chips
fighting on the same bus for the textures and get right back into a memory
bandwidth limitation again.
Not only would this force you to use DDR, but would also severly limit the
scalability of the chipset.

> The only advantage of separate memory sets is that each set contains only
half of frame buffer memory. But the gain is not
> big enough. Even 40MB of DDR SDRAM would already serve better than 64MB of
> SDRAM divided into two 32MB blocks (thats at 1280x1024x32b, tripple
> buffered). 40MB of DDR is certainly cheaper than 64MB of non-DDR.

The entire advantage of the seperate memory banks is to allow SLI operation.
A side benefit is the huge amount of bandwidth you gain.  How the
framebuffer is distributed is irrelevant.
I dont believe DDR can be bought at 40MB.  Only 32 and 64MB.  According to
manufacturers, their 32MB DDR GeForce's cost ~$100 more than their 32MB SDR
versions.   They also cost more than what 3dfx currently has as an MSRP for
the 64MB V5.
Since SDR prices are quite inflated due to artificial reasons, as well as
the quake, it should be a good bit less when the card comes out.
You also have to consider the speed of the memory.  The GeForce DDR uses a
low speed DDR chip (150Mhz, 300 effective) because the Geforce chip is not
running at a high speed.   For a Voodoo5 5500 and especially 6000, they
would need much faster DDR.  That means even more $$$.
In the configuration 3dfx has, the V5 5500 has more memory bandwidth than
DDR anyway.  The 6000 has a much higher bandwidth.
All that matters is speed.  I dont care how 3d card manufacturers get the
speed, just that it is there.