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NVIDIA's GeForce FX 5700 Ultra with GDDR3


Tomorrow's memory today
— 12:00 AM on March 25, 2004

WAY BACK in October of 2002, ATI announced GDDR3, a third-generation memory specification designed for point-to-point graphics implementations. GDDR3 was developed by ATI in collaboration with a number of leading DRAM manufacturers, but it's an open spec that others are free to use. The new memory type will likely be featured in next-generation graphics products from both ATI and NVIDIA, but NVIDIA is also rolling out GDDR3 a little early in a new version of the GeForce FX 5700 Ultra.

Although the GeForce FX 5700 Ultra is already familiar, NVIDIA's new spin of it provides an early look at GDDR3's potential for graphics implementations. Read on to see what GDDR3 does for the 5700 Ultra, and what the new memory type could do for next-gen graphics products.

The card
Despite using swanky new memory chips, NVIDIA's GeForce FX 5700 Ultra with GDDR3 is almost indistinguishable from the old DDR2 card.


GeForce FX 5700 Ultras with DDR2 (top) and DDR3 (bottom)


GeForce FX 5700 Ultras with DDR2 (top) and DDR3 (bottom)


GDDR3 courtesy of Samsung

From above, the two GeForce FX 5700 Ultras look identical. However, flipping the cards reveals that the new 5700 Ultra uses only four memory chips, all of which are mounted on the front of the board. The DDR2 version of the FX 5700 Ultra splits a total of eight memory chips between the front and back of the board and requires an heat sink to keep the rear-mounted chips cool.

NVIDIA tapped Samsung to provide the memory chips for this 5700 Ultra card. The K4J55323QF-GC20 chips are rated for operation at clock speeds up to 500MHz and run on only 1.9V. For comparison, the original FX 5700 Ultra's memory chips were only rated to run at 450MHz and required 2.5V.

Higher clock speeds and lower power consumption highlight the main benefits of GDDR3 memory over DDR2, but the FX 5700 Ultra only scratches the surface of GDDR3's capabilities. Samsung currently makes GDDR3 chips rated for operation at speeds up to 800MHz—300MHz faster than its best DDR2 chips. And even at 800MHz, Samsung's GDDR3 chips don't require more than 1.9V.

Although NVIDIA isn't using exotic 800MHz GDDR3 chips with the FX 5700 Ultra, GGDR3 does give the new GeForce FX 5700 Ultra little more juice. The new card's memory clock speed has been increased to 475MHz, or effectively 950MHz once we take DDR memory's clock-doubling scheme into account, giving it a slight memory bandwidth edge over its predecessor.

 Core clock (MHz)Pixel pipelines Peak fill rate (Mpixels/s)Texture units per pixel pipelinePeak fill rate (Mtexels/s)Memory clock (MHz)Memory bus width (bits)Peak memory bandwidth (GB/s)
GeForce FX 5700 Ultra475419001190090612814.4
GeForce FX 5700 Ultra GDDR3475419001190095012815.2

The GDDR3-equipped GeForce FX 5700 Ultra still has a 128-bit memory bus, so the boost in memory bandwidth only works out to about 800MB/sec. Of course, it's possible this slight increase in peak theoretical bandwidth could be offset, at least in part, by higher memory access latencies with GDDR3. (We don't have an exact means of measuring memory latencies on a graphics card, unfortunately.) Also, NVIDIA isn't fiddling with core clock speeds for the new 5700 Ultra, so its theoretical pixel and texel fill rate peaks are unchanged.