A Closer Look
As expected, AMD is using a relatively complex cooler that uses large copper heatsinks for GPU cooling. It also cools secondary components like the memory chips, voltage regulation circuitry and PCIe bridge chip.
The HD 7990 includes a blackplate, unlike the GTX 690 and GTX Titan. In this case, the backplate also provides cooling to the memory chips on the back of the card.
The card requires two 8-pin PCI-Express power cables for operation. This power configuration is good for up to 375 W of power draw.
A little green LED on the back of the card lights up when the second GPU is in ZeroCore/ULPS sleep mode. All three fans will still be running in that state, so the LEDs are the best way to check if ZeroCore is active.
Just like on other HD 7900 Series cards, the HD 7990 includes a dual-BIOS feature that toggles between the normal BIOS and a backup BIOS for both cards. This acts as an extra safeguard in case something goes wrong during a BIOS flash.
It's nice to see Volterra voltage controllers back on recent graphics card. The two Volterra VT1556 controllers handle one GPU each, providing monitoring features and software control via I2C.
The GDDR5 memory chips are made by Hynix and carry the model number H5GQ2H24AFR-R0C. They are specified to run at 1500 MHz (6000 MHz GDDR5 effective).
The PEX8747 48 lane PCI-Express Gen 3 Bridge chip is the latest in PLX's arsenal of PCIe bridge chip solutions. It is used to link the two GPUs and connects them to the rest of the system.
AMD's Tahiti graphics processor introduced the GCN shader architecture. It is also the first GPU to be produced on a 28 nm process at TSMC. The transistor count is 4.31 billion.