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Cooling System Design and Performance

You may have already noticed that the Radeon HD 5750 and HD 5770 have completely different coolers. The former card has a simple black aluminum heatsink with a 9-blade 80mm impeller. The Radeon HD 5770’s cooler consists of a heatsink, a blower, a separate aluminum plate for memory chips, and a plastic casing.

 

Dark-gray thermal grease is used as a thermal interface for both GPUs. The Radeon HD 5750’s cooler uses a 2-pin connection but notwithstanding this fact the fan speed is adjusted by the card automatically depending on the GPU temperature. The Radeon HD 5770 has a blower from AVC with a 4-pin connection and PWM-based speed adjustment.

 

The blower is driving the air through a small aluminum thin-ribbed heatsink. The ribs are placed 2 millimeters apart and soldered to the copper base which is encircled by a copper heat pipe. The pipe’s job is to distribute the heat uniformly in the heatsink base.

I tested the efficiency of these coolers in a closed system case. The room temperature was 24°C. The cards were loaded by FurMark 1.7.0 running in stability check mode at 1920x1200. The frequencies and temperatures were monitored withMSI Afterburner 1.4.1.

First let’s see how effective the coolers are in automatic fan management mode.

 

Curiously enough, the GPUs clocked at considerably different frequencies prove to have the same temperature under load, which is the consequence of the cards’ using different coolers. The Radeon HD 5770’s cooler is expectedly more effective although its blower works at 49% speed as opposed to the HD 5750’s 45% speed.

Then, I tested the cards at the full speed of their coolers.

 

The Radeon HD 5770 is more effective than the Radeon HD 5750 in this case, too. The HD 5770 is noisier than the HD 5750, but I will discuss the noise factor later.

I hadn’t enough time to test one pair of cards, so I only tried to overclock one Radeon HD 5770 and one HD 5750 (with their default coolers and in a closed system case). As a GPU stability check, I ran OCCT’s GPU test and two scenes from 3DMark 2006. I also made sure the graphics memory was stable by running two 3DMark 2006 scenes with 8x full-screen antialiasing and three heavy 3D games. Increasing the GPU voltage to 1.2V, I managed to overclock my XFX Radeon HD 5750 to 855/1425MHz (805MHz at the default voltage) and XFX Radeon HD 5770 to 960/1420MHz (910MHz at the default voltage).

 

The temperatures of the graphics cards did not change much after overclocking but the coolers were working at higher speeds than at the default frequencies.

 

I had six alternative cooling systems at hand but could not install any of them on the Radeon HD 5750 and 5770. The distance from the center of the GPU die to the aluminum screen of the DVI outputs is a mere 60 millimeters on both cards, so the coolers’ heatsinks just pressed against that screen and could not be installed. Considering that the GPU is so close to the graphics cards’ outputs, it is going to be hard to select an alternative cooler. By the way, the diagonal distance between the cooler’s mounting holes in the PCB is 61 millimeters.

Finally, I can show you a photo of two Radeon HD 5750 cards installed inside the system case and connected in CrossFireX mode:

 
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