|MSI R6870 Radeon HD 6870 Video Card|
|Reviews - Featured Reviews: Video Cards|
|Written by Bruce Normann|
|Friday, 05 November 2010|
Page 4 of 18
MSI R6870-2PM2D1GD5 Detailed Features
The full PWM-based voltage regulator section that supplies power to the HD 6870 GPU is shown here. It is a 4-phase design that is controlled by a relatively new chip: the CHL8214 from CHiL Semiconductor Corporation. It is a dual-loop digital multi-phase buck controller specifically designed for GPU voltage regulation. Dynamic voltage control is programmable through the I2C protocol. CHil's first big design win in the graphics market was with a slightly meatier 6-phase chip in the GTX480 Fermi card, a power monster if there ever was one. The CHL8214 is a 4+1 design, but I don't see where the "extra" controller loop is used. It looks like the sense inputs for the "+1" controller are just tied to ground.
Here's one phase of the VRM section, and a closer look at the 4+1 PWM controller chip. MSI is currently not supporting voltage control for the CHL8214 with their Afterburner software, but I suspect it will only be a matter of time before it is included in a new release. According to Alexey Nicolaychuk, creator of RivaTuner, "Development is in progress."
The VRM section also features another new chip in this application space; a DrMOS design that includes both the driver transistors and the High-Low MOSFET pair in one tightly integrated package. It's positioned right below the R22 choke in the image above. It's a very small device, with markings of 59901M, and it's so new I can't find any specs for it. This chip doesn't look at all like a typical power semiconductor; they usually have large solder pads that serve as thermal paths for heat transfer out of the inner metal layers of the device. The entire underside of the chip must be completely covered with solder pads in order to make it work without burning itself up. It saves a huge amount of board space though, which is critical in this unusual layout, where the designers have moved the VRM section to the flip side of where it's usually located; it is now situated between the GPU and the output connectors. A full complement of discrete MOSFETs and drivers for low side and high side circuits would not have fit in this area of the board.
There are no open-frame power supply chokes in this design; so that potential cause of high pitched noise has been eliminated at the source. The board is fed from two 6-pin PCI-E power connectors exiting the top edge of the fairly long card. There should be no problems fitting this card in any standard ATX style chassis.
The PC board had excellent solder quality and reasonably good precision on 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 board was about average for cleanliness, compared to some of the samples I've looked at recently. There were some traces of residue across different sections of the board, but they weren't excessive. 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. You can take some solace in the fact that the environmental cost to produce this board was less than one that comes out of the anti-static bag sparkling clean.
There are two more power supply controller chips used on the MSI R6870 to provide the correct voltage to the memory banks and other subsystems. One is a uP6122AF chip from UPI Semiconductor. It is a Single-Phase Synchronous-Rectified Buck Controller with 2-Bit VID Input control. This IC does not support I2C software voltage control, and it remains to be seen whether the BIOS provides its own software control to interface with the controller at the hardware level. We'll have to wait for the next release of MSI's Afterburner to find out. The second controller is an APW7165 from Anpec Electronics and it's responsible for the voltage supply to the memory chips. It's been used on a number of popular graphics cards already, like the NVIDIA GeForce GTX460, 465 and 470, and I've seen it used on a Radeon HD 5830 as well. It's also a single-phase controller without software voltage control, and like the uP6122AF, uses integrated driver transistors to push a conventional, discrete pair of MOSFET outputs.
The memory choice for the MSI R6870 is consistent with the AMD reference designs. The basic Radeon HD 6870 specs only require 1050 MHz chips for the memory, but these Hynix H5GQ1H24AFR-T2C GDDR5 parts are designed for up to 1250 MHz. The 1250 MHz Samsung chips on the HD 5xxx series of Radeon cards have been mediocre overclockers; we'll have to see if these Hynix parts are a little more willing to exceed their ratings.
Now that we've had the grand tour of the MSI R6870, 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.