Closer Look: PowerColor PCS+ HD 6870

The PowerColor PCS+ HD 6870 1GB GDDR5 is based on the AMD reference card, but it is not identical. The board layout is the same, but one card has a few more power supply chokes, the other has one or two more MOSFETs in the smaller VRM sections, and the PowerColor board has a different hardware arrangement for providing power to the cooling fan. I think the phrase; "Six of one and half a dozen of the other..." applies here. All of that only applies after you get down to the board level though. Let's start at the top.

The first thing you notice when you pick up this video card is that it's fairly light; it's not dense and solid like the reference card. The single fan is an axial type, placed at the center of the card, near the GPU location. The fan pushes air down through the main opening and it spreads out through the fin assembly and down to the component level on the PC board.

The fan shroud is the antithesis of a completely sealed-off design; there are vents all over the black plastic cover. The overall styling is modeled after the general layout of ultra-performance sport cars, right down to the headlights and the wheel well vents on the fender. The fan is a basic DC-powered design with a 3-wire electrical connection for a tachometer output signal, but the RPM of the fan was not reported to various monitoring and control utilities, just the percentage.

We will see later that there has been a major change to the board layout, which avoids the dreaded overheating of the VRM section that plagued the HD 5870 reference design. The main voltage regulator modules have been relocated to the end closest to the I/O plate. After the GPU itself, these voltage regulator chips are the things that benefit the most from active cooling. The axial design of the cooling fan pretty much guarantees that they are getting decent airflow in this design, and the shroud does nothing to prevent that. The memory also benefits from direct airflow, but my experience with GDDR5 memory is that it runs pretty cool all by itself.

With high-end video cards, the cooling system is an integral part of the performance envelope for the product. Make it run cooler, and you can make it run faster, has been the byword for achieving gaming-class performance with all recent GPUs. Even some midrange models have turned out to be supreme overclockers with enhanced cooling. The PowerColor PCS+ HD6870 1GB GDDR5 has a fairly straight forward design for its cooling, compared to other high-end reference designs released for the HD 6870. The thermal load for this new Barts GPU is lower, so the cooler doesn't need to use all the tricks in the book to keep temperatures down. The PCS+ models from PowerColor have always sported decent overclocks and excellent cooling performance, so I'm expecting good results.

The layout of the various elements of the cooler design is a little easier to see in this straightforward view from the GPU's perspective. An oversized copper block mates with the GPU and transfers heat directly to the three copper heatpipes running directly over the center of the GPU.

Two 8mm and one 6mm diameter heatpipes are soldered between the copper mounting plate and the aluminum fin assembly, with all three pipes closely spaced and passing directly over the center of the GPU die. Once they exit from there, they spread to the outer reaches of the aluminum fin assembly. This cooler uses traditional assembly techniques, with solder firmly attaching the pipes to the fins and the GPU interface plate. The solder also acts as a reasonably good heat conductor, and electronics manufacturers are intimately familiar with soldering things together, so it's a tried and true assembly technique.

The thermal interface material (TIM) was very evenly distributed by the factory, but was applied slightly thicker than necessary. One day, anxious manufacturing engineers are going to figure out that too little TIM is better than too much. For the rest of us who end up correcting these things, a thorough discussion of best practices for applying TIM is available here. I have never had the thermal performance of a video card degrade after I've taken it apart and reassembled it with a smaller amount of high quality TIM paste.

The layout on the front and back of the printed circuit board is somewhat unusual in the arrangement of its power supply components. Most cards keep the current paths as short as possible by grouping the power distribution and voltage regulator module sections somewhere between the power input connectors and the major electrical loads, which are the GPU and the memory modules. With a radial blower on the reference design, there is a dead spot directly behind the blower wheel where there is very little airflow. This is exactly where the VRM section usually ends up, and these components can generate some serious heat. The HD 6870 flips the main VRM section over to the left side of the board, and makes the DC power come ¾ of the way down the length of the card and then do a U-turn before heading into the GPU. I can just see all the electrical engineers doing the face-palm.... Of course, they ultimately gave in, rather than redesigning everything after de-rating all the components due to the higher expected temps. The axial fan on this card doesn't require this arrangement, but it isn't handicapped by it either.

This new mid-range card from AMD is not as simple and cheap to produce as the GTX460 design, which is its current Fermi-based competitor. It's also not as compact, but it still runs cool and doesn't use as much power as its direct ATI performance twin, the HD 5850. It is however, simpler and less costly to produce than the GTX470, which is also its near neighbor in terms of performance, if not price.

In the next section, let's take a more detailed look at some of the new components on this non-reference board. I did a full tear-down, so we could see everything there is to see...

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