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Radeon HD 6850: PCB Design and Cooling System

The junior model of the new series is somewhat shorter than its cousin but its power connector is located at the shorter rather than longer edge. Thus, the Radeon HD 6870 and 6850 will have roughly the same dimensions with the power cable attached. The cooler’s casing is designed in the same angular style.

There is nothing interesting we can see until we remove the cooler. Like the senior model, the Radeon HD 6850 has only one CrossFire connector.

As opposed to the Radeon HD 6870, this card has a traditional component layout with the power subsystem residing at the back. Despite the lower clock rate and voltage of the GPU, the GPU voltage regulator has four phases, too.

Like on the senior model, a CHL8214 controller from CHiL Semiconductor is responsible for managing the GPU voltage regulator.

The memory voltage regulator is the same as well, based on an uP6122 chip. These components are located at the front of the PCB. The Radeon HD 6850 has only one external power connector, which is 6-pin, too. Thus, it is going to load the power section of the PCI Express slot more than the Radeon HD 6870, but it has a lower GPU voltage in 3D mode: 1.05 instead of 1.175 volts. The PCB design doesn’t provide for an 8-pin power connector.

We’ve got the same memory chips here as on the Radeon HD 6870: Hynix H5GQ1H24AFR-T2C with a rated frequency of 1250 (5000) MHz. Such chips are rather redundant for the Radeon HD 6850 because this card’s standard memory frequency is only 1000 (4000) MHz. Coupled with the 256-bit memory bus, this ensures a memory bandwidth of 128 GBps. The total memory amount is 1024 megabytes. The card drops its memory clock rate to 300 (900) MHz in power-saving mode.

The GPU marking looks different than that of our Radeon HD 6870. The last line is printed in a different font while the first line, which denotes the manufacturing date, has a letter U. We don’t have a smallest inkling as to what this might mean, but we know that this Barts was manufactured a week later than the Barts installed on our Radeon HD 6870.

The GPU configuration is identified correctly by our software tools. We can only add that the Radeon HD 6850 has 48 active TMUs out of the physically present 56. Like with the other card, MSI Afterburner cannot control the GPU voltage but shows that the power-saving technologies work correctly: the GPU clock rate is lowered to 100 MHz and the memory clock rate to 300 (900) MHz when the card is idle. The graphic core of the Radeon HD 6850 doesn’t have to work at high frequencies, so its voltage is set at 1.05 volts by default.

The junior Radeon HD 6800 series card has the same interfaces as the senior model: two DVI-I and two DisplayPort connectors with support for DP++ and daisy-chain connection. It also has a version 1.4a HDMI port. The card’s single CrossFire connector allows combining two Radeon HD 6850 cards into a single multi-GPU subsystem. Asymmetric configurations with Radeon HD 6870s may be supported as well.

The cooling system of the Radeon HD 6850 is similar to the above-described cooler of the Radeon HD 6870 but simpler: the heatsink is smaller and has only one flat U-shaped heat pipe in its base. The size of the heatsink is far from impressive really. Like on the Radeon HD 6870, the cooler’s casing is shaped in such a way as to drive some of the air towards the side panel of the computer case.

A figured plate with low fins is an additional element of the cooling system. It cools the memory chips and power components, contacting with them via thermal pads. The plate is fastened to the PCB separately from the heatsink and plastic casing.

This cooling system overall doesn’t look capable of performing wonders, either, especially as it has a smaller fan, but the GPU of the Radeon HD 6850 has lower voltage and frequency settings than the same GPU on the Radeon HD 6870. We’ll check out the efficiency of these coolers in the next section of our review.

 
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