Sapphire Radeon HD 7790 Dual-X OC Reviewccokeman - March 21, 2013
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Sapphire HD 7790 Dual-X OC Closer Look:
Sapphire's HD 7790 Dual-X OC is a dual slot video card designed for use in a 16x PCIe slot-equipped motherboard. PCIe 3.0 is supported with backwards compatibility to ensure the widest user base. This dual slot cooling solution-equipped video card measures 8.5 inches in length, providing fitment in a larger range of chassis. From the top view you can see the configuration of the dual 11-blade fan cooling solution called Dual-X. This is a two slot cooling solution that pushes air back into the chassis as well as outside it. In the past this design has proven successful. On the back side of the PCB there is not much of interest save for the left end of the card being barren of any surface mount components. The side views shows the cooling solution size and how much of the PCB it covers.
Display connectivity includes a pair of DL-DVI ports, a full size DisplayPort, and a single HDMI 1.4a port that supports 3D and HD audio. Eyefinity is supported on up to three screens with the HD 7790, although three screen gaming is most likely going to require a second card in Crossfire. The back end of the card is open to allow the card to discharge some of the thermal load generated into the chassis. Most modern chassis have enough airflow to handle this additional thermal load.
Crossfire support on the Sapphire HD 7790 Dual-X is available with up to a two card configuration. If you need more performance than this, AMD's 7XXX series product stack is full of cards that can get you there. A single 6-pin PCIe power connector is used to supply the additional 75 watts needed in addition to the power supplied by the PCIe slot. The minimum power supply size recommended for a system equipped with the HD 7790 is 500 watts. Typical board power falls in the 85 watt range, a figure proven out in the power consumption tests.
Sapphire's Dual-X cooling solution consists of an aluminum fin array with a pair of heat pipes pulling the thermal load from the GPU core out to the fin array for discharge through the shroud and out of the chassis. It extends almost the length of the PCB from end to end. The dual heat pipes run directly over a copper contact plate that sits right over the 28nm Bonaire core yet is not a direct heat pipe contact design. The memory is cooled by way of the auxiliary cooling plate/mounting bracket. Thermal material is used to bridge the gap between the GDDR5 ICs and the contact surface.
Airflow through the heatsink is what cools the GPU and memory on this card, much like just about every video card on the market. A pair of 70mm 11-blade fans provide this airflow. These fans are similar to the dust-proof fans found on the Vapor-X lineup and provide a long life. Surprisingly, this iteration of the fan is much quieter when running at over 4000 RPM than most. When controlled by the VBIOS the fans are inaudible.
AMD used a new revision of its Graphics Core Next architecture, codenamed Bonaire, on the HD 7790. This iteration is built on a 28nm process with 2.08 billion transistors under the hood. Specifications include 896 stream processors that handle two primitives per clock, 56 texture units, 16 ROPs, and 1GB of GDDR5 VRAM running through a 128-bit bus. A total of four memory ICs from Hynix are used that support speeds of up to 1500MHz. Baseline clock speeds from AMD are 1GHz on the GPU core and 1500MHz on the GDDR5 memory. Sapphire tweaked these quite a bit to get the end user a boost clock of up to 1075MHz on the core and 1600MHz on the memory. A significant boost over the base lines. Stripped down to the core there is not much to cover on the PCB. The VRM circuit is towards the front of the card and is cooled by way of an aluminum heat sink in the fan airstream.
Equipped with an excellent cooling solution and a serious boost in clock speeds over the reference design, Sapphire's Dual-X HD 7790 OC should have some added muscle when it comes time to flex it.