|Gigabyte GeForce GTX 480 SOC GV-N480SO-15I|
|Reviews - Featured Reviews: Video Cards|
|Written by Bruce Normann|
|Wednesday, 22 December 2010|
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Gigabyte GV-N480SO-15I Detailed Features
Besides the upscale cooling system, which is yards ahead of the reference design, the Gigabyte GTX 480 Super Over Clock has an impressive selection of voltage regulator sections that supply cleaner power than the average video card gets. The input and controller sections are in their traditional place, at the far end of the card. The PWM-based voltage regulator section that supplies power to the HD 6870 GPU is based on the ADP4100 Programmable Multi-Phase Synchronous Buck Converter. It is a 6-phase design that is was initially designed for Intel CPU voltage regulation. Voltage control is digitally programmable through an 8-bit VID for an output range of 0.375 V to 1.6 V. The 6 phases then get split up into 12 phases and then 12 separate sets of driver, high-side, and low-side MOSFETS do the actual power switching. Purists will complain that this is not a "True" 12-phase design, but the truth is, the GPU doesn't care how the individual phases get generated, it is seeing twelve phase power. There may not be as many discrete steps available for throttling back when the GPU only needs low power, but this card isn't really optimized for saving power; it's meant to run as fast as possible.
The other two chips in the image above are an 8-Bit CMOS Microcontroller and a GPIO Controller with 14 outputs and SMBusTM interface. This is the computer that runs all of the low-level functions on the video card. As far as I know, no one has tried to overclock it yet...
The driver transistors for the main VRM section are on the top side of the card, in the general vicinity of the biggest heat generator, so they get additional cooling via this thin aluminum heatsink. It's held on with a spring clip, that's quite a bit stiffer than you might think at first glance. The totem-pole style output MOSFET pairs are on the back side, and the solid-core chokes and polymer capacitors are on the top side along with the drivers. There's nothing really new and innovative in this design so far, but it's very well executed with a lot of attention to detail, and has lots of headroom available for higher voltage and current levels.
The VRM section also features some heavy duty film capacitors on the output that are specially designed to eliminate the last vestiges of noise on the critical DC supply to the GPU and DRAM. These large, flat units from NEC-Tokin have the strange name "Proadlizer", which stands for prompt broadband stabilizer. They are rated for 2.5V and each has a capacitance of 900 μF. That's about twice the capacitance as any of the twelve solid polymer units on the top side of the board, but it's not the total capacitance that matters, it's how well they work at the highest frequencies.
Every electronic component has some extra characteristics that are sometimes referred to as parasitic values. All resistors have parasitic capacitance and inductance, and all capacitors have extra resistance and inductance. The critical thing is that these deviations from perfect behavior are frequency dependant. For a capacitor, they tend to reduce its effectiveness at higher frequencies. Each of the various types of capacitor are optimized for different frequency ranges, and film caps, like these Proadlizer units, are best at higher frequencies. You can see from the manufacturer's data that these are optimized for reducing noise the 100 MHz range, but they are still effective out to 1.0 GHz.
A new trend I am seeing on the latest video cards is the switchover to SMD packaging for the crystal oscillators. Both NVIDIA and AMD have moved away from the traditional through-hole mounting style for this component. These were one of the last holdouts in the transition to full SMD production. Check out the miniature welding around the perimeter of this 27 MHz can; for size reference the entire package is 3mm x 6mm.
The PC board had excellent solder quality and precision component placement, as can be seen below. This is the area on the back side of the board, directly below the GPU, and it's one of the most crowded sections of any graphics card. On my LCD screen, this image is magnified 20X, compared to what the naked eye sees. The small SMD capacitors located side-by-side in this view are placed on 1mm centers. This is one of the most critical sections of the PCB for build quality, as variations in stray capacitance here could impact the performance of the GPU, and certainly its overclocking ability.
This Gigabyte board was well above average for cleanliness, compared to some of the samples I've looked at in the last year. There were some minor traces of residue on different sections of the board, but they were minimal compared to what I've been seeing lately. It's obvious that this card was not made in the same factory as the others I've tested recently. Once you start looking at macro photographs like this, there's no place for any manufacturing shortcuts to hide. All manufacturers are under intense pressure to minimize the environmental impact of their operations, and cleaning processes have historically produced some of the most prolific and toxic industrial waste streams. The combination of eco-friendly solvents, lead-free solder, and smaller SMD components have made cleaning of electronic assemblies much more difficult than it used to be.
The memory choice for the Gigabyte GTX 480 SOC is consistent with the NVIDIA reference designs. The basic GTX 480 reference specs only require 924 MHz chips for the memory, but most cards have been using these Samsung K4G10325FE-HC04 GDDR5 parts, which are designed for up to 1250 MHz. This Gigabyte Super Over Clock version only takes the memory up to 950 MHz, out of the box. It's nice that there is some headroom left on the memory chips, but the GPU has to be willing to play at these higher frequencies, too.
Now that we've had the grand tour of the Gigabyte GTX 480 SOC, inside and out, it's time to put it to the test. Well, Benchmark is our first name, so don't worry. There are a wide variety of tests waiting for you in the next several sections, including some new entries. Let's start off with a complete description of the Video Card Testing Methodology.