The Heatsink

Although the 7800 GT consumes less power than 6800 Ultra, it is still a very hot card. It needs a good cooler to dispel the prodigious amount of heat produced.

But instead of sticking to the bulky dual-slot solution used in the 6800 Ultra, NVIDIA used a single-slot cooler, similar to that used in the 6800 GT. Take a look at just how slim this cooler is.

Single slot cooler

The heatsink is made entirely of aluminium. But unlike the more complicated two-piece design used in the GeForce 7800 GTX, the 7800 GT cooler uses a smaller, single-piece design.

Base of the heatsink

As you can see from the picture above, the GPU was protected by a copper shim attached to the base of the cooler. The memory chips were all attached to the base of the heatsink using thermal tapes.

The Fan

The fan used is a 3.36W ADDA fan, running at 12V with a current draw of 0.28A. Our first impression when we started up the system was the lack of noise from the fan.

The fan

Unfortunately, this fan was just as annoying as the fan used in the 6800 Ultra. It had a loud whine at start-up, but the fan spun down once the driver was loaded.

Even during 3D-intensive situations, the fan did not appear to spin up to handle the greater thermal load. As a result, the heatsink got really hot to touch!

The Video Decoder Chip

The GeForce 7800 GT used the SAA7115 PAL/NTSC/SECAM video decoder chip from Philips Semiconductors.

Video decoder chip

This video decoder chip supports the following features :

Video acquisition

• Six analog inputs, internal analog source selectors (e.g.: 6 x CVBS or (2 x YC and 2 CVBS) or (1 x YC and 4xCVBS))
• Two built in analog anti-alias filters
• Two improved 9-bit CMOS analog-to-digital converters
• Fully programmable static gain or automatic gain control (AGC) for the selected CVBS or Y/C channel
• Automatic Clamp Control (ACC) for CVBS, Y and C
• Switchable white peak control
• Requires only one crystal (32.11 MHz or 24.576 MHz) for all standards
• Independent gain and offset - adjustment for raw data path
   

Comb filter video decoder

• Digital PLL for Synchronization and Clock Generation from all Standards and Non Standard Video Sources e.g. consumer grade VTR
• Automatic detection of 50/60Hz field frequency, and automatic recognition of all common broadcast standards
• Enhanced Horizontal and vertical Sync Detection
• Luminance and chrominance signal processing
• Improved 2/4-line comb filter for two-dimensional chrominance/luminance-separation operating with adaptive comb filter parameters.
• Independent Brightness Contrast Saturation (BCS)
• User programmable sharpness control
• Detection of copy protected input signals and level according to Macrovision standard
• Automatic TV/VCR detection
• 10 bit wide video output at comb filter video decoder
   

Video Scaler

• Horizontal and vertical down-scaling and up-scaling to randomly sized windows
• Horizontal and vertical scaling range: variable zoom to 1/64 (icon)
• Vertical scaling with linear phase interpolation and accumulating filter for anti-aliasing (6-bit phase accuracy)
• Conversion to square pixel format
• Generation of a video output stream with improved synchronisation grid at the I-Port
• Two independent programming sets for scaler part
• Fieldwise switching between decoder and expansion port (X-port) input
• Brightness, contrast and saturation controls for scaled outputs