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PCB Design and Specifications

This version of Radeon HD 5850 is based on the reference PCB design and uses a reference cooler developed by AMD’s graphics department. As a matter of fact, this is true for all other Radeon HD 5800 series cards available today. We described this design in detail in our article called "Hidden Threat": ATI Radeon HD 5850 Graphics Card Review. The only distinguishing feature of the XFX product is the sticker on the cooler’s casing. The PCB itself is almost 4 centimeters shorter than the Radeon HD 5870’s one as we already wrote in an earlier review.

 

 
XFX Radeon HD 5850 Black Edition (left) and ATI Radeon HD 5870 reference (right)

So, you shouldn’t worry that this card may be too long for your system case. The XFX Radeon HD 5850 Black Edition can be easily installed into any computer enclosure, save for the most compact models. The power circuit follows a 3+2 design. Thus, the GPU power section has one phase less than on the Radeon HD 5870 but this should be more than enough for the RV870 core considering the Radeon HD 5850 specs.

The GPU voltage regulator is based on a Volterra VT1165MF controller that provides the option of software voltage control. Theoretically, this should help overclockers avoid volt-modding the card, which is a dangerous thing to do. But practically, the most reckless of overclockers still combine both methods to squeeze some more megahertz and a few hundred 3DMark points from the poor graphics card. Such experiments often end disastrously, but the risk cannot stop an inveterate overclocker!

As opposed to the Radeon HD 5870, the Radeon HD 5850 has only one VT1156MF controller. Additionally, there is a VT237WF chip that combines the control and power sections of the voltage regulator which seems to be responsible for the RV870’s memory controller. The memory chips are powered by the pair of tiny chips from the same maker marked as VT243WF. The configuration and placement of the power connectors is different, too. Here, we have two 6-pin connectors installed at the shorter edge of the PCB whereas the Radeon HD 5870 has them at the top, longer edge. This may make it easier to connect the PSU cables if the card is already installed into the system case.

There are eight Samsung K4G10325FE-HC04 chips on the PCB, the same as you can find on the Radeon HD 5870. These GDDR5 chips have a capacity of 1 Gb (32 Mb x 32), a voltage of 1.5V, and a rated frequency of 1250 (5000) MHz. The Radeon HD 5850 has a specified frequency of 1250 (4500) MHz which raises its peak bandwidth to 144 GBps. The memory bus is 256 bits wide and the total amount is a standard 1024 megabytes.

The GPU marking says that this sample of RV870 was manufactured on the 39th week of the last year. As usual, there is no other practically useful information in it. Two out of the 20 SIMD arrays available in the RV870 are turned off on the Radeon HD 5850, so the total amount of active ALUs and TMUs is 1440 and 72 as opposed to the Radeon HD 5870’s 1600 and 80. Like the memory chips, the GPU of the XFX card is pre-overclocked from the reference frequency of 725 MHz to 765 MHz, which is a promise of a nice performance boost in games. But considering that Radeon HD 5850 cards use those RV870 samples that did not pass the frequency test and/or have defective subunits, we don’t expect the card to be able to overclock much above its default clock rate.

Like the senior cousin Radeon HD 5870, the XFX Radeon HD 5850 Black Edition can output video content to three monitors simultaneously but one of them has to have a DisplayPort. Besides two DVI-I connectors and one DisplayPort, the card has a native HDMI port, so you don’t have to use an adapter to connect a plasma or LCD TV-set. The card can output audio over HDMI in various formats including multi-channel HD formats, which is so far the unique feature of the ATI Radeon HD 5000 series. The two CrossFireX connectors allow uniting up to four cards in multi-GPU mode, but there are few mainboards that would allow installing as many as four dual-slot graphics cards simultaneously.

As for the cooling system, the XFX is equipped with the Radeon HD 5850’s reference cooler which is a smaller and slightly revised version of the Radeon HD 5870’s cooler.

The heatsink is smaller and has only two heat pipes instead of the four pipes in the Radeon HD 5870’s cooler. Besides, the heatsink is not part of the base and is not physically connected to it. A layer of dark-gray thermal grease ensures proper thermal contact between the heatsink’s copper base and the GPU die. The rest of the components that require cooling contact with the aluminum frame through two types of thermal pads: 3-layer elastic sandwiches with a filling of gel-like white grease for the memory chips and dry, brittle green pads for the power circuit elements.

The heatsink is cooled by a FD9238H12S blower from NTK (HK) Limited. The 12V fan has a power consumption of 0.8A, which is quite a lot. The fan is very noisy at its maximum speed, but it may only reach that maximum in the hands of extreme overclockers. In ordinary mode, its speed is PWM-regulated automatically and the card is overall not very loud. Like with the Radeon HD 5870, the partitions in the cooler’s casing turn a part of the air flow by 90 degrees to drive it through the slits in the card’s side and into the system case. The rest of the hot air is exhausted outside through the slits in the card’s mounting bracket. The latter is populated so densely that this compromise is unavoidable.

Overall, the cooling system of the XFX Radeon HD 5850 Black Edition uses a reliable and time-tested design that has proved effective on earlier graphics cards from both AMD and Nvidia. We have no worries that it may not cope with its job or be too loud, especially as we covered this issue in a previous review. However, the XFX Radeon HD 5850 Black Edition is pre-overclocked by its manufacturer, so its GPU and memory chips produce more heat. Therefore, we should check out how well this cooler works under these harsher conditions.

 
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