ASUS HD 7970 DirectCU II Reviewccokeman -
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HD 7970 3GB DirectCU II Closer Look:
ASUS's HD 7970 is more than an exercise in looks and cooling performance – it is based upon AMD's 28nm 'Graphics Core Next' Tahiti core architecture and packed full of features that improve longevity, voltage control, and overclocking margins. Measuring 11 x 5.1 x 2.1 inches, the HD 7970 DirectCU II is going to fit into majority of cases on the market. The most identifiable feature of this card is the 2.5-slot DirectCU II cooling solution that employs a pair of fans to cool not only the GPU, but the rest of the onboard components. The back of the PCB uses a back plate that gives additional support for the PCB. A cutout above the GPU core socket provides room for ASUS's SAP capacitor. The back plate identifies this card such that when installed in a chassis with a side window, you can easily show off exactly the beast of a graphics card you are running. The bottom and top have additional venting for the airflow provided by the dual dust-proof fans. ASUS's HD 7970 DirectCU II supports usage in PCIe 2.0/3.0 16x slots.
Connectivity options on the ASUS HD 7970 Direct CU II include a single-link DVI-I port, a dual-link DVI-D port, and a quartet of full-sized DisplayPort connections. Together, the card will allow support for up to six displays in an Eyefinity 6 configuration. HDMI connectivity is through the use of an included adapter. Much of the thermal load is discharged through the opening above the display connections, though I expect some to escape through the openings in the shroud, into the chassis. Fear not, just about every modern chassis should have enough case airflow to minimize or eliminate this additional thermal load. The back end of the card is sealed, directing airflow forward and out. Along the PCB is the large durability frame used to stiffen the PCB and spread the thermal load across a greater area, providing improved cooling to the components on the PCB.
A pair of Crossfire bridge connections means the ASUS HD 7970 DirectCU II supports up to 4 cards in a CrossfireX configuration. However, the 2.5x-slot DirectCU II cooling will preclude this option without switching to either full-cover liquid cooling blocks or liquid nitrogen pots. You will also need a motherboard that can provide the needed 16x PCIe slots such as the ASUS Rampage IV Extreme. A Dual BIOS switch is also in place, in case you need to reflash the vBIOS. A pair of 8-pin PCIe power connections at the back end of the PCB help provide up to 375 watts to the 12-phase power circuit and DIGI+ VRM controller. Most of us have been in a rush to fire up that new video card only to receive a warning message on the screen or annoying beeping that lets us know something is just not right. As part of ASUS protective design strategy, the HD 7970 DirectCU II is equipped with the VGA LED feature that provides a visual indication of the state of the power connections. Red means the connection is not complete and Green means that all is good and it's fraggin' time.
Across the top and back of the PCB is one of the more interesting features of the ASUS HD 7970 DirectCU II. Here, VGA Hotwire is used to monitor and control the voltages supplied to the video card when connected to select motherboards including ASUS Rampage IV Extreme and Maximus V Extreme. VGA Hotwire uses simple solder pads on the pack side of the PCB that connect to the motherboard via soldered-on wiring. As a result, you get improved range and more precise hardware level control of the core, memory, and phase (PLL) voltages, possibly netting you the maximum clock speed that software controls just cannot provide.
Under the shroud, we get a look at what the DirectCU II cooling solution is all about. The DirectCU II cooling solution is a two piece aluminum fin array with 6 heat pipes that works in conjunction with ASUS's durability frame and the back plate to provide a rigid and efficient platform to control temperatures. ASUS uses a total of six flattened copper heat pipes that contact the GPU core through a solid copper contact plate. The thermal load is then passed through the heat pipes to a pair of aluminum fin arrays. Four flow into the rear fin array while two feed into the front array. ASUS's durability frame is then used to cover the DIGI+ VRM circuit and 3GB of VRAM. The large frame is going to offer enhanced cooling due to its large dissipation area.All of this is then actively cooled by a pair of thick dust-proof 10cm fans that look to offer 600% mroe airflow than the reference cooler design. As thin as the fin arrays are, the entire combination works well. If you choose the ASUS HD 7970 DirectCU II as your weapon of choice for some sub zero cooling, ASUS includes, as part of the accessory bundle, a heat sink that can be mounted on the VRM circuit. ASUS's Durability frame has this area integrally mounted so when it is removed, the VRM is left uncovered. Mounted on the PCB with push pins, this heat sink is fairly beefy and should definitely deliver cooling potential that is 20% cooler and 14dB quieter than a reference cooling solution.
The fans ASUS has chosen for this application are made by Everflow and carry part number T129025SU. These 9 blade fans run on 12V and when paired together, push 600% more airflow through the shroud than you get with the standard HD 7970 reference cooling solution. As part of ASUS's protective designs, these fans feature a 25% increase in lifespan by way of their "Dust Proof" design. This fan design is sealed in two areas to significantly reduce dust intrusion into the fan and motor hub that otherwise ends up reducing the RPM of fans to a failure point. If left untreated, failed fans can lead to the failure of a GPU outright due to running overheated.
Once all of the cooling solution and back plate parts are removed, you can get a clear look at the PCB and installed components. ASUS's DirectCU II series video cards are equipped with ASUS's own SAP (Super Alloy Power) VRM design that is designed to be more efficient, run cooler, reduce EMI, and handle a higher current load for improved overclocking margins. The central feature on the front of the PCB is the 12-phase VRM. At the back end of the card, we also find ASUS's Super Alloy chokes, Super Alloy capacitors, and Super Alloy MOS. At the back end of the PCB is the DIGI+ VRM controller that orchestrates the voltage applications. On the back side of the PCB directly under the GPU socket is the where the SAP CAP is located, to ensure the GPU gets a steady diet of current without dips that can otherwise reduce overclocking margins.
Rather than explain the nuances of ASUS SAP design, here are a few slides to illustrate the feature set. These parts are the base of the card and will rarely be seen or understood. However, these are what makes the card tick, long term. When you look at feature set, Super Alloy Power and DIGI+ VRM are points of difference when compared to competitors' designs.
The HD 7970 DirectCU II is built upon the 28nm Tahiti core with a transistor count of 4.31 billion, a stream processor count of 2048, 128 texture units, 32 ROPs, and 3GB of GDDR5 memory running through a 384-bit bus. The standard HD 7970 DirectCU II has a core clock speed of 925MHz, while the TOP version gets a higher binned core capable of 1000MHz out the door. 3GB of Hynix GDDR5 modules, part number H5GQ2H24MFR-R0C, are used on the HD 7970 DirectCU II. These modules, running at 1375MHz, are rated to run at 1500MHz and have become a proven commodity. I have seen these modules overclocked in excess of 1700MHz in the past.
Fully equipped to run cooler, quieter, and faster than the competition, the ASUS HD 7970 DirectCU II looks to be capable of making a run as one of the top cards on the market.