PCB Design and Features
The face side of the Sapphire Radeon HD 7870 OC is covered by the already familiar Dual-X cooler.
The card’s model name can be read from a sticker on the edge of the cooler’s plastic casing. You can see the cooler’s thick heat pipes from the opposite side.
The card measures 253x106x39 millimeters, which is in fact equal to the reference AMD Radeon HD 7870. The Sapphire Radeon HD 7870 OC is equipped with one dual-link DVI-I, one HDMI 1.4a, and two mini-DisplayPorts:
As you can see, there’s a vent grid above the connectors in the card’s mounting bracket. It is used to exhaust the hot air from the cooler out of the system case.
As the reference Radeon HD 7870, the Sapphire version has two 6-pin power connectors and one MIO connector for building CrossFireX configurations out of two such cards.
Contrary to our expectations, the PCB follows the reference design.
Its power system, located between the video connectors and the GPU chip is formulated as 5+1+1 (GPU + memory + PLL):
It is managed by a CHiL Semiconductor CHL8225 controller.
The card’s 28nm Pitcairn XT GPU was manufactured on the sixth week of 2012 (early February):
The GPU contains 1280 unified shader processors, 80 texture-mapping units and 32 raster back-ends. Unlike the reference AMD Radeon HD 7870 GHz Edition which clocks its GPU at 1000 MHz, the Sapphire version is pre-overclocked by 5% to 1050 MHz. The GPU voltage of our card was rather high at 1.218 volts in 3D mode although the GPU quality level is 82.7% (it’s quite high according to the ASIC quality test). The GPU clock rate is dropped to 300 MHz in 2D mode and its voltage is lowered to 0.893 volts then.
There are eight FCBGA-packaged chips of GDDR5 memory from Hynix Semiconductor on board the Sapphire Radeon HD 7870 OC for a total of 2 gigabytes.
The barely visible marking reads H5GQ2H24MFR T2C, which translates into a rated clock rate of 5000 MHz. The Sapphire version really clocks its memory at 5000 MHz, which is 200 MHz or 4.2% higher than the reference card’s specs. The memory frequency is lowered to 600 MHz in 2D mode. The memory bus is 256 bits wide.
Here is a summary of the Sapphire Radeon HD 7870 OC specs: