Specifications, board analysis

So what’s changed with the GeForce 7800 GTX 512MB? Quite a bit.

While the board is still 100% based on NVIDIA’s G70 GPU with 24 pixel pipelines and eight vertex shaders, NVIDIA’s bumped up the clock speeds dramatically. The graphics core is clocked at 550MHz, that’s 120MHz higher than the GeForce 7800 GTX 256MB. This change improves fill-rate from 10.3Mtexels/second to 13.2Mtexels/sec, an improvement of over 20%.

On the memory side, things are even more exciting, as NVIDIA’s reference specifications call for a speed of 850MHz. That’s 250MHz higher than the GeForce 7800 GTX, improving memory bandwidth by 16GB/sec alone, from 38.4GB/sec in the 7800 GTX 256MB, to 54.4GB/sec in the GeForce 7800 GTX 512MB. To put things in perspective, NVIDIA’s current mainstream offering, the GeForce 6600 GT, has 16GB/sec of peak memory bandwidth total. We’ve provided the following chart, which summarizes the changes:

High-End Graphics Comparison
	GeForce 7800 GTX 512MB	GeForce 7800 GTX 256MB	RADEON X1800 XT	GeForce 7800 GT	RADEON X1800 XL
Core Clock (MHz)	550	430	625	400	500
Memory Speed (MHz)	850	600	750	500	500
Memory Interface Width	256-bit	256-bit	256-bit	256-bit	256-bit
Memory Size & Type	512MB GDDR3	256MB GDDR3	256MB GDDR3 & 512MB GDDR3	256MB GDDR3	256MB GDDR3
Memory Bandwidth (GB/sec)	54.4	38.4	48	32	32
Pixel Fill Rate (Gpixels/sec)	8.8	6.88	10.0	6.4	8.0
Texel Fill-Rate (Gtexels/sec)	13.2	10.3	10	8.0	8.0
Pixel Pipelines	24	24	16	20	16
Vertex Units	8	8	8	7	8

GeForce 7800 GTX 256MB reference board and 512MB reference board

Dual-slot cooling

As a result of the new speeds, power consumption is up slightly. Whereas the GeForce 7800 GTX is rated at 100W peak power consumption, the 7800 GTX 512MB is rated at 120W peak. NVIDIA recommends at least a 350W power supply with 22 amps on the 12V rail for single card operation, while NVIDIA recommends a power supply with at least 500W and 30 amps on the 12V rail for SLI. These are the same guidelines NVIDIA recommends for the GeForce 7800 GTX 256MB.

To hit such high speeds, NVIDIA says that they’ve tuned the G70’s fabrication process to speed up certain data paths inside the chip. NVIDIA has also made a few tweaks to the GeForce 7800 GTX 512MB’s PCB design to facilitate the higher clocks. The most notable change you’ll spot though is the GeForce 7800 GTX 512MB’s new cooler.

The reference board up close

As you can see in the pictures, NVIDIA has outfitted the GeForce 7800 GTX 512MB with a completely different cooling unit than its predecessor. This is actually the exact same heatsink/fan unit NVIDIA and PNY use on the high-end Quadro FX 4500 workstation boards. (Leadtek also uses this same cooler on their WinFast PX7800 GTX TDH MyVIVO Extreme card.)

Fan up close

The back of the board - no memory modules here

Bottom edge of the board

The cooler starts with a copper baseplate, which rests directly over the GeForce 7800 GTX 512MB’s G70 graphics core. Heat is then transferred from the copper plate to an array of long, aluminum-based heat pipes. Inside each of the heat pipes is distilled water. As the GPU begins to heat up, the distilled water in the heat pipe begins to boil, forcing hot vapor to the other end of the heat pipe where it is cooled. From there the vapor condenses back to the liquid phase and returns to the other end of the heat pipe. This cycle is continually in motion, working to keep the graphics core cool.

The heat pipes and heatsink

A closer shot

Long, tall fins on heatsink

Helping to keep all this cool is a hefty dual-slot heatsink/fan unit, which is composed of aluminum. The heatsink itself is massive, nearly swallowing up the entire 7800 GTX 512MB board. It has dozens of long, tall fins, further increasing its surface area. NVIDIA then finishes the cooler off with a large cooling fan. Air from the fan passes out the sides of heatsink, including outside the system case.

With such a large fan onboard, you may think that the GeForce 7800 GTX 512MB generates a considerable amount of noise, however the opposite is actually the case. In operation, the fan runs nearly silent, the heatsink/fan unit on our Athlon 64 FX-57 CPU actually ran louder than the GeForce 7800 GTX 512MB! This is easily the quietest fan we’ve ever seen on a high-end NVIDIA reference board, and will give Arctic Cooling’s VGA Silencer series a run for its money in the noise department. But it doesn’t stop there, in addition to the new cooling system, NVIDIA outfits the 7800 GTX 512MB board with 900MHz memory modules, giving overclockers a little bit more headroom in their overclocking endeavors.

Heat pipes up close

The top of the card

One last shot of the bottom

Some of NVIDIA’s board partners will no doubt use this to provide factory overclocking. We’ve already received XFX’s GeForce 7800 GTX 512MB card, and sure enough it was clocked higher than stock, sporting a core clock frequency of 580MHz (30MHz over default) while its memory was running at 865MHz (15MHz over stock).