After the initial installation the heatsink was immediately removed and the contact area was inspected. Even with the rather thick preapplied thermal paste the contact is excellent. On the core you can see the ATI logo shine through which is a good indicator of contact quality. Getting the heatsink off the card took a lot of force which is further proof of good contact.
For the overclocking tests I used my ATITool overclocking utility version 0.25 Beta 11. On the X1000 series artifact scanning isn't working (yet), so I used several tests including 3DMark2003 and 2005 to test for artifacts.
Temperature was measured with one case side open by reading the on-die thermal diode of our ATI Radeon X1800 XL PCI-Express. Idle temperature was measured after letting Windows sit one hour at the desktop. Load temperature was measured after running 3DMark2003 looped for one hour. Both at the card's default clock of 500 / 495 MHz.
On the X1800 the fan speed is varied based on temperature. The stock fan was running at 73% under load and 36% when idle. To have another value to compare to, I used ATITool to force the stock fan to always run at 100%.
Arctic Silver Lumière was used as thermal interface material for the GPU core in all installations. Lumière is a specially engineered testing compound - it needs no settle in time to reach its maximum performance, but it's not designed for permanent use. I compared the temperatures with Lumière against the temperatures of the included thermal paste and saw a difference of less than 1°C. So it is safe to say that there will be no improvement in using another thermal paste like Arctic Silver 5.
Radeon X1800 XL PCI-E | Maximum Core Clock | Fan Noise | Temperature Load | Temperature Idle |
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Stock cooler - dynamic fan | 564 MHz | 46 dbA | 67°C | 57°C |
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Stock cooler - fan 100% | 567 MHz | 62 dbA | 64°C | 47°C |
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Accelero X2 - dynamic fan | 571 MHz | 34 dbA | 58°C | 43°C |
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Accelero X2 - fan 100% | 573 MHz | 44 dbA | 50°C | 42°C |
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Accelero X2 - fan 100% 1.3V GPU voltage | 595 MHz | 44 dbA | 60°C | 47°C |
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Wow, the Accelero X2 cools so much better than the XL stock cooler. I would assume that the temperatures will be better than the XT stock cooler as well.
While the overclocking did not increase that much, the gains were there, and with a lucky card might be even higher.
Using the GPU voltage control in ATITool should help get a higher overclock out of your card. I could safely increase the GPU voltage to 1.30V from the default of 1.05V and load temperatures didn't increase too much. With the stock cooler, even 1.20V gave me well over 80°C, something I wouldn't consider safe. With increased voltage the card ran fine at 595 MHz.