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Closer Look at ATI Radeon HD 5870

PCB Design

The Radeon HD 5870 is nothing extraordinary on the outside even though it does look cool and stylish due to the new black casing of the cooling system. The narrow red strip crossing it is a nice touch in the product appearance and a point for AMD’s designers.

The back part of the card is covered by a metallic plate which does not perform any function because there are no elements requiring much cooling there. It is simple to dismantle the cooling system: you only have to undo the screws on the reverse side of the card and the couple of screws on the mounting bracket. And then you will see the following:

The Radeon HD 5870 has a surprisingly simple PCB design for a graphics card with such advanced specs as it has. The back part where we usually find GPU and memory power circuitry looks somewhat empty. At least, there is a lot of free room around the Volterra VT1165MF controller. The GPU voltage regulator has four phases, and there are seats for elements of a fifth phase on the PCB.

The two top phases with single inductors and other power packs seem to relate to the memory voltage regulator. One more Volterra VT1165MF controller is located in an unusual place near the CrossFireX connectors. It seems to be responsible for powering the card’s memory.

The Volterra chips provide for a more flexible power management by ATI PowerPlay technology. Some AMD partners will probably offer the user the opportunity to increase the GPU and memory voltages from software. Overclockers would appreciate this feature as they wouldn’t have to volt-mod the card in order to achieve the same result. There are two 6-pin PCIe 1.0 power connectors on the PCB which indicates a rather low power draw of the RV870. However, the installation of an 8-pin PCIe 2.0 connector is possible.

The card carries eight GDDR5 memory chips from Samsung (K4G10325FE-HC04) with a capacity of 1Gb (32Mb x 32), voltage of 1.5V, and a rated frequency of 1250 (5000) MHz. They work at a reduced frequency of 1200 (4800) MHz on the Radeon HD 5870. Coupled with the 256-bit memory bus, the card’s memory bandwidth is 153.6GBps. That’s quite high in comparison with previous-generation single-chip cards but the dual-chip Radeon HD 4870 X2 and GeForce GTX 295 have a memory bandwidth of 230.4GBps and 224GBps, respectively. It means the Radeon HD 5870 may be slower in some resource-consuming games like Crysis at high display resolutions.

The new chip resembles the R600 externally because its die, like the R600 die, is turned around by 45 degrees. Despite the horrendous complexity, it is rather small at only 334 square millimeters, thanks to 40nm manufacturing process. The die is protected with a metallic frame on the GPU package. The marking says this sample of RV870 was manufactured rather recently, on the 33rd week, i.e. in mid-August, of 2009.

The new version of GPU-Z knows about the RV870 and reports the same info about the Radeon HD 5870 as AMD’s official specs. The core indeed has 1600 ALUs grouped into 20 SIMD cores, 80 texture processors, 32 raster back-ends and is clocked at 850MHz.

The ordinary Radeon HD 5870 can output video content to three monitors simultaneously, so it has two DVI-I ports, one HDMI and one DisplayPort. The rest of the mounting bracket is perforated for ventilation. The Radeon HD 5870 supports CrossFireX and offers two appropriate onboard connectors. Theoretically, you can unite four such graphics cards into a single graphics subsystem that would deliver unprecedented performance in modern and upcoming games.

 
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