PCB Design and Specifications
This Radeon HD 5870 does not have anything in common with the reference design. It features an original PCB with thicker metallization layers (the so-called “2oz Copper PCB” technology) and colored differently than the reference PCB.
Gigabyte did not use a cooler that would exhaust the hot air out of the system case. Instead, there is a cooling system with two large fans similar to what we saw in our Palit GeForce GTX 470 review. Such coolers are generally rather effective but not if there are other add-on cards nearby which block one of the fans. As usual, the most interesting things are hidden beneath the heatsink:
The PCB space is utilized more efficiently than on the reference card: there is almost no free room at the back of the Gigabyte Radeon HD 5870 SO. The GPU power circuit is considerably reinforced using six rather than four phases.
Overclockers will appreciate the opportunity to monitor the card’s voltages at the control points located in the bottom right corner of the PCB. We can also note that the card uses high-quality chokes with ferrite cores.
An ADP4100 chip from On Semiconductor is responsible for managing this complex power system. The same chip is used on GeForce GTX 275 cards. Software-based GPU management is implemented via the Gigabyte OC Guru utility. You also see NEC/Tokin 0E907 film capacitors with a capacitance of 900 µF that look like memory chips, and six SMD LEDs indicating the operation of the GPU voltage regulator. When the latter is working normally, the indicators are green.
The above-noted film capacitors are also employed in the memory voltage regulator. Some of its components are in the back part of the PCB while others are near the CrossFire connectors. Oddly enough, both power connectors the graphics card has are of the 6-pin variety whereas the original design from AMD provides for one 8-pin PCIe 2.0 connector with double load capacity. Well, as we found out, single-processor RV870-based cards have no real need for such 8-pin connectors.
There are eight GDDR5 memory chips from Hynix on the PCB, marked as H5GQ1H24AFR-T2C. The same chips with a capacity of 1 Gb (32 Mb x 32) each are installed on Radeon HD 5970 cards. The T2C suffix means their ability to be clocked at 1250 (5000) MHz and this is indeed the memory frequency of the Gigabyte Radeon HD 5870 SO, delivering a peak memory bandwidth of 160 GBps. This is higher than the reference card’s 153.6 GBps but lower than the GeForce GTX 480’s 177.4 GBps. The difference isn’t huge, however, and even negligible considering the weaker texture-mapping subsystem of the GF100 processor.
The graphics card automatically lowers its memory frequency to 960 (3840) MHz in power-saving mode. Compared with the reference card from AMD, which lowers its memory frequency to 300 (1200) MHz, this is not very economical, but graphics memory does not contribute much to a graphics card’s overall power draw.
Like any other Radeon HD 5870, this version has the following GPU configuration: 1600 ALUs grouped into 20 SIMD cores, 80 texture-mapping processors and 32 raster back-ends. The RV870 chip of our sample of the card was made on the 7th week of 2010. It is marked just like any other such core, but Gigabyte culls the best chips for its Super Overclock series, capable of working at increased frequencies. The testing procedure is rather gloomily referred to as GPU Gauntlet. Here, the core clock rate is increased from 850 to 950 MHz and its voltage is raised from 1.15 to 1.18 volts. You can use the Gigabyte OC Guru tool to raise the voltage even higher, but this didn’t help us in our experiments. The card is less economical than the reference one in power-saving mode, lowering its GPU frequency to 680 MHz instead of 157 MHz. Thus, the Gigabyte Radeon HD 5870 SO is going to be less economical in desktop applications and during HD video playback.
Like the reference Radeon HD 5870, this card has two DVI-I connectors, one HDMI and one DisplayPort. And like the reference card too, it allows connecting three display devices simultaneously, but one of them must use the DisplayPort. Besides, it has a couple of CrossFire connectors for building a graphics subsystem with up to four graphics cards. For example, we ran our Gigabyte Radeon HD 5870 SO together with a Radeon HD 5970 without any problems.
The cooling system employed by Gigabyte does not look like the reference one but is similar to the cooler we saw on the Palit GeForce GTX 470. A couple of rather aggressive-looking 80mm Everflow T128010SH fans are blowing at the big flat aluminum heatsink connected with four heat pipes to the copper base.
Most of the hot air remains inside the system case. The heat-exchanger that contacts with the GPU die is ordinary enough and does not use the direct-touch technology. Standard dark-gray thermal grease serves as a thermal interface. The rest of the components lack any heatsinks and are cooled by the air flow. Despite the larger dimensions, the whole arrangement is secured on the PCB with only four spring-loaded screws. So, we wouldn’t recommend you to take this card by the cooler’s casing lest you should damage the GPU die.
The design of the cooler is quite familiar to us already and we know that it can cool the GPU effectively. However, it requires that the system case itself be properly ventilated. And it doesn’t work that effectively if there is a neighboring add-on card blocking one of the fans. If you install a Gigabyte Radeon HD 5870 SO into your system, you must make sure the expansion slot beneath it is empty or occupied by a small card. Otherwise, the left fan won’t be of much help, dropping the efficiency of the whole cooler. We’ll test that efficiency in the next section.