Waarom de 3dfx Voodoo5 geen DDR geheugen heeft

Bij Voodoo Extreme is een leuk verhaal te vinden over waarom de 3dfx Voodoo5 eigenlijk geen DDR geheugen gebruikt, in tegenstelling tot nVidia's GeForce 1 en 2. Hieronder het verlossende woord van 3dfx's Alf Covey:

[Q] Seeing as the Voodoo 5 boards have to repeat the textures in RAM twice, is it true that if they were equipped with DDR SGRAM, it would be possible to see up to a 200% performance boost in memory bandwidth and/or overall performance? And if that's true, wouldn't it alleviate retail prices and raise your profit margin by including (slightly more expensive) less DDR SGRAM vs (even more expensive) double the SDRAM (i.e. 32mb DDR SGRAM vs 64mb SDRAM)? This sounds as if it would make the boards slightly more affordable for consumers and yet deliver performance equal to or better than what the boards will probably deliver on the shelves and *still* allow you to deliver a version of the V5 6000 (using 64mb of DDR SGRAM rather than 128mb of SDRAM) that falls far under the currently expected $600 retail price and yet still completely outperforms The Competition's 2nd Gen product while retaining fantastic eye-candy with 4xFSAA (at a lower price)?

[A] The DDR does increase memory bandwidth but for it to be useful, you need to be in a bandwidth-limited case before it will make a difference. When an application is limited by memory bandwith then increasing the memory bandwidth will, of course, increase the frame rate. DDR (dual data rate) memory can ideally transfer data at twice the rate of SDR (single data rate) memory and will be an excellent graphics memory in the future. However DDR memory is currently very, very expensive, almost 2X the cost of SDR memory, therefore it has limited usefulness in mainstream PC applications. 3dfx has chosen to increase memory bandwidth by using wider memory interfaces constructed with standard SDR memory. By running two VSA-100 chips in parallel as we do on the Voodoo5 5500 we have the same memory bandwidth per frequency as a GeForce DDR. Actually we have a higher effective bandwidth because of some inefficiencies that exist in accessing data in DDR memories.

The Voodoo5 6000, with 4 VSA-100 chips and effectively a 512-bit memory interface has more than twice the memory bandwidth of a GeForce2 running at the same memory clock speed. In a nutshell, DDR may be direction to head in the future but right now the SDR architecture on the VSA-100 is the most efficient way to go both in performance and price.

Thanks GaMeOvEr voor de tip.