Cooling System and Temperatures
Now let’s check out the cards’ coolers and temperatures. Each is equipped with a dual-slot cooler of classic design: a blower is driving the air through a heat-pipe-based heatsink installed on the GPU and exhausting some of it out of the system case. Some of the air is left inside, though.
The cooling systems differ as we could make sure after dismantling them both.
So, there is a blower inside each cooler. It is installed on a metallic plate that serves as a heatsink for the power components and memory chips. The similarity ends here. The heatsink consisting of four 6mm heat pipes and aluminum ribs is soldered to the base plate on the Radeon HD 5870 whereas the heatsink of the Radeon HD 5850 is an individual element. It consists of a copper base about 4 millimeters thick, two 8mm heat pipes and aluminum plates that hang on the pipes and are additionally soldered to the base.
Besides, there is a flat heat pipe in the metallic plate right above the power components. It has no heatsink and helps distribute heat more uniformly in the plate. This solution doesn’t seem effective to us.
The coolers of both cards are equipped with 92x38mm blowers with PWM control.
The Radeon HD 5850’s cooler has a FirstD FD9238H12S fan whereas the Radeon HD 5870 comes with a fan from NTK (HK) Limited marked as FD9238H12S, too.
We guess the fans only differ with the stickers. Their speed is PWM-regulated from 1100 to 4800rpm (according to monitoring tools). We will compare their noise with those of other graphics cards shortly.
Right now we’ll show you how effective these coolers are. We tested them in a closed system case (its exact configuration is listed in the next section). The room temperature was 23.6-23.8°C during this test. The cards were loaded by FurMark 1.7.0 running in stability check mode at 1680x1050. The frequencies and temperatures were monitored with MSI Afterburner 1.2.0.
First let’s see how effective the reference coolers of Radeon HD 5850 and 5870 cards are in automatic fan management mode.
Bravo, AMD/ATI! Besides being effective, the coolers are never faster than 31% of their full speed even under FurMark, producing moderate noise. Our and other reviewers’ criticism of the reference coolers of Radeon HD 4870/4890 in 3D applications must have been heard by ATI engineers who have developed efficient and low-noise coolers. The GPU of the Radeon HD 5870 was no hotter than 76°C in FurMark and less than 65°C hot in 3DMark (at 28% cooler’s speed). The graphics cards were not audible in the quiet system case in 2D mode.
Next, let’s check out the coolers at 50% and 100% speed.
The coolers are much louder, of course, but the temperature of the Radeon HD 5850’s GPU lowers from 74 to 57°C at 50% speed and to 52°C at 100% speed. The temperature of the GPU of the Radeon HD 5870 lowers from 76°C to 60°C at 50% speed and to 53°C at 100% speed.
The distance between the mounting holes of the Radeon HD 5850 cooler is the same as on the Radeon HD 4870/4890 (75.5 millimeters), so you can try to install an alternative cooling system on this card. For example, a Thermalright T-Rad2 with two 92mm fans (1500rpm).
Unfortunately, a Thermalright VRM1(2) heatsink could not be installed on the voltage regulator elements of this card because the latter’s mounting holes are placed 3 millimeters wider than on the Radeon HD 4870/4890. Anyway, the alternative cooler easily coped with the GPU even without that additional heatsink.
The voltage regulator components were not hotter than 92°C then, which is lower than with the Radeon HD 4890 where they could be as hot as 110 or even 120°C. When the card was equipped with its reference cooler, these components were only 72-75°C hot.
Considering the low temperature and the reduced frequencies of the Radeon HD 5850 in comparison with the HD 5870, we had some hopes for good overclocking. We checked this out using the reference cooler, MSI Afterburner and AMD GPU Clock Tool. As a stability test we ran FurMark and the FireFly Forest scene from 3DMark06 with highest settings.
First, we tried to run the Radeon HD 5850 at the frequencies of its senior counterpart Radeon HD 5870:
Our Radeon HD 5850 found it easy to work at 850/4800MHz. Moreover, the GPU was stable at 910MHz with the default voltage of 1.087V! This was already an excellent result but we went further. After a couple of hours we found that the highest stable GPU frequency was 1010MHz at 1.21V voltage! We could not get higher by increasing the voltage more. Anyway, this is an impressive result. The memory chips overclocked less successfully, being stable at 4960MHz.
Interestingly, the overclocked card has a GPU temperature of only 67°C under load (this test was performed at 50% cooler’s speed).
Our Radeon HD 5870 was less successful at overclocking. We increased its memory frequency higher, to 5200MHz, but the maximum GPU frequency was only 905MHz. The GPU did not react to our increasing its voltage (up to 1.3V stepping 0.02V), so we had to stop at 905/5200MHz.