|PowerColor AX6990 4GBD5-M4D Video Card|
|Reviews - Featured Reviews: Video Cards|
|Written by Bruce Normann|
|Sunday, 20 March 2011|
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PowerColor Radeon HD 6990 Detailed Features
Each GPU gets its own PWM-based VRM power section, with an independent 4-phase supply delivered directly to each Cayman-class GPU. The power MOSFETs and their driver transistors are integrated into a DrMOS design from Volterra, although I don't think they use that name for their products. They're the eight shiny IC packages below the large white inductor modules. The power supply chokes for the GPU circuit are from Cooper Bussmann, one of the oldest trade names in the power component business. AMD is using these modular chokes on almost all their high power reference designs lately; I think they first showed up on the HD 5870.
There are two Volterra VT1556 PWM controllers mounted on the back side of the PCB, providing all the high level voltage control functions. This part is a holdover from the Radeon HD 6950 and HD 6970 reference cards, where only one controller was required for the single GPU. The controller offers I2C communication and control, so someone will undoubtedly build an interface into their monitoring and control software. The fact that every HD 6900 series card uses the same controller pretty much guarantees it.
The memory and the PCI Express bridge chip get their power from a smaller set of PWM power supply sections located in the center again, only along the bottom edge. The individual filter chokes can be seen at the top of the image above, and it looks like the memory is getting 2-phase power with the PCI Bridge getting a single-phase. Speaking of the bridge chip, it is a re-branded PLX item, and is the same part that was used on the Radeon HD 5970 card. I'm guessing that AMD had a large stock of them from previous orders, because they still have the ATI logo on them.
This little switch is what unlocks the power of this card, literally. The board ships with the switch in position 2, where it limits the GPU core clock speed to 830 MHz, and the core voltage to 1.120 volts. Capping those two parameters keeps the overall power consumption at or below 375 watts, which is technically all the various connectors are supposed to be able to supply. It also keeps the heat down, to where the fan is not overly loud in order to keep the GPU temps below 80C in continuous gaming use. If you want to take it further, you first have to remove the yellow warning sticker which refers you to the product manual for all the dire consequences that can occur if you proceed. Once you agree to void the product warranty and flip the switch to position 1, the GPU clock is automatically bumped up to 880 MHz and the default GPU core voltage goes up from 1.120V to 1.175V.
WARNING: AMD's product warranty does not cover damages caused by overclocking, even when overclocking is enabled via AMD software and/or the Dual-BIOS Function on the AMD Radeon HD 6990. This restriction is carried through by PowerColor and almost every other AMD AIB partner.
All of the reference Radeon HD 6990 cards feature 4GB of GDDR5 frame buffer memory, and surprisingly, the memory modules used are the lower speed devices that were previously seen on the HD 6950. The Hynix H5GQ2H24MFR-T2C components are rated at 1250 MHz and can reach 5.0 Gbps bandwidth with a 1.5V supply, which is what AMD is using in this application. The stock Radeon HD 6970 cards have a 1375 MHz memory clock, and require the "-ROC" version of this chip to run at that speed.
The PC board had good solder quality and precision component placement, as you can also above. I've not seen this much bare traces before on any card; most times the solder flows over the entire pad, leaving nothing exposed. It's not a case of not enough solder being used for the joints, each connection I see has an ample amount to serve its dual function of holding the part in place and an electrical connection. 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 smallest SMD capacitors located in this view are placed on 1mm centers. The board surface was also quite clean, which is always a good thing.
The I/O plate has a new configuration that is optimized for both airflow and multi-monitor display setups, AKA Eyefinity. By putting all the display connectors in one row, the size of the cooling vent could be maximized, which is critical for this high-powered beast. The use of all mini Display Port connections allowed a total of five connections, although only four can be active at any one time. PowerColor includes three miniDP adapters in the package: 1-Passive miniDP to Single Link DVI, 1- Active miniDP to Single Link DVI, and 1-Passive miniDP to HDMI. That's an impressive collection of adapters, which should help all of us who are just getting used to Display Port and still require support for legacy monitors.
Before we move into the testing phase of the review, let's take a detailed look at the features and specifications for the new AMD Radeon HD 6990 video card. AMD and PowerColor have supplied us with a ton of information, so let's go....