🚀 go-pugleaf

Freon wrote in message <383cb50e.0@news.mocc.net>...
>
>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.

Could you, please, first read my letter, before replying?
If chips share memory the SHARE textures, too. There is no point in
duplicating exactly the same data if memory is shared.


>
>> 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,

That's the point. If they USED shared DDR instead of duplicated non-DDR
they'd have cheaper solution.

> but would also severly limit the
>scalability of the chipset.

They simply waste memory. Now they are going too sell 64MB cards screasming:
Wow! 64MB RAM card! Average Joe would go for it and buy it, even if cheaper
card with ~40MB memory would be in all aspects better. At 1280x1024x32 with
tripple buffer 24 MB of that memory is wasted for duplicated textures. At
lower resolutions even more is wasted.

>
>> 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.

V5 will be released in few months. GeForce should be available now. So you
pay a premium forn the fastest available. And few months from now DDR will
be cheaper, too.

>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.

As well DDR prices are.


>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 $$$.

DDR is not inherently much more expensive than SDR. Access time for memory
cell, etc is the same for particular SDR and two times faster DDR. The main
difference lays in interface logic, and that chips are internally divided
into two interleaved banks.

>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.


V5 6000 will be hell expensive. I see no reason for buying it other than
'mine is bigger attitude'. V5 5000 will have the same bandwidth as it would
have with single DDR RAM intead of double SDR RAM.

Regards
                              Sebastian Kaliszewski
--
"Never underestimate the power of human stupidity" - from Notebooks of L.L.