ATI Radeon X800 XL Overclocking

The two cards use quite different cooling solutions, as was discussed in the roundup. Club3D make use of the familiar reference cooler for the Radeon X800 XT Platinum Edition, while Sapphire use a cooler that bares similarities to MSI’s Radeon X800 SE cooler, and also to the revision 2 cooler for the invisible Radeon X700 XT.

The cooler on Club3D’s X800 XL is in fact a very similar design to the reference X800 XL cooler, with the only difference being in the fan design. The fan is capable of reaching a 20% higher RPM than the reference cooler. For those with alarm bells ringing, the fan will only increase its speed when the GPU temperature is high enough to require it. This overhead of cooling can be used for overclocking or improving the stability when the system temperature is high. Club-3D’s fan is a clear fan with several white LED’s, while the reference design uses a standard black fan. We doubt that makes a fat lot of difference to the cooling capabilities of the heatsink design, because the design is based on a large slow-moving fan that pushes air over the GPU core with relative silence.

Taking the clock speeds that we achieved with each card’s stock cooling solution during our recent X800 XL roundup as the starting point for our investigation, we pinged ATI for some thoughts on whether the X800 XL suffered from lack of power when overclocking. As you will know, overclocking success is a card-by-card business, and there are no guarantees that you will be able to reach the clock speeds that we attained with the stock coolers, never mind with additional cooling.

The answer that came back from ATI was a slightly mixed thought path, but it is hard to come up with an exact answer without actually seeing what happens when we reach the stability threshold where artefacts begin to appear.

In this particular case, the supplemental power certainly could aid the overclocker, but that's not a guarantee. Whether to include the extra power jack or not is a build option that is left up to the board manufacturer to decide.

Extra power can help if you intend to push significantly beyond the stock clocks, but you wouldn't necessarily get to clocks that are high enough to make this a big issue. Then again, you might. In either case - your warranty will have disappeared!

It is possible that the limits you reached are related to power consumption - but they could just as easily be thermal. To give an exact comment would require our lab guys in Canada to see the situation for themselves with the video card covered in temperature probes. Normally, when a board is pushed to its cooling limits, it will start to show pixel corruptions but won't necessarily lock-up straight away.

Also, what happens when the power and/or thermal limits are reached will vary from board to board.

Once again - we really don't recommend overclocking products without express/written confirmation from the AIB that this is possible!

We also gathered some thoughts on the matter from both Sapphire and Club3D - they offered quite different views, and this reflects the final X800 XL implementations from both companies too.

We spoke to Sapphire at CeBit 2005, and they stated that their card did not require an additional power connector, and that they were not planning on implementing one in the future to appeal to the overclockers and enthusiasts out there.

On the other hand, Raymond Koning from Club3D provided us with a whole host of information regarding why the choice was made to add the additional power connection:

Normally, as I was told, the X800 XL is consuming just a little below 75Watts. Consumption may vary since memory configurations are subject to change, like the quality of the VPU. One of the problems with high performance graphics is memory availability and PCB design. When VGA cards are more advanced, more research is required to develop a reliable PCB. Do not underestimate the importance of a reliable PCB, since that is currently one of the most critical parts of high performance graphics. If a design has itself proven, we can slightly change that to make it fit in the next product.

Second, we are not so happy with putting 75Watts through a mainboard PCB. Since this means you are completely dependent to the quality of the power that is delivered to your VGA cards by your mainboard.

Mainboards are, just like some VGA cards, subject to cost down projects from certain manufacturers, which means replacing components for cheaper versions to save some money. We are having bad experiences with mainboard manufacturers when it comes to noiseless power regulation. Components become overheated since heatsinks are removed, and certain power regulators are replaced for less qualified models. Some mainboards are not completely matching the specifications resulting in crashing or not functioning VGA cards. Since the current X800 XL is so close to the maximum specs we decided to add an external power connection to avoid problems with poor mainboard designs.

Third, even if the power regulation is ok, I still do not like the idea of putting 75Watts through a mainboard... But this is just a personal issue since the specs do allow this.

Basically, Club3D were slightly worried that some motherboards, or indeed power supplies, would not be able to deliver enough power through the PCI-Express x16 interconnect, and thus causing problems with the video card. You cannot remove the possibility of these problems occurring completely, but by adding an extra power connector you significantly reduce the chances of the problem occurring.

With a high quality motherboard and power supply, this means that there is a greater chance of achieving a higher overclock, because the source of power is not limited to just the PCI-Express x16 interconnect. Remember that overclocking is a bit of a lottery, though. There are no guarantees that you will get a video card that clocks very well, whether it has an additional power connector or not.

Bearing all of this information in mind, we thought that it would be a good idea for us to test whether the limits of the two cards were related to the card reaching its thermal limits. Thus, we used an Arctic Cooling ATI Silencer 5 on the two video cards to see whether our overclocking attempts could be improved thanks to an improved cooling solution. At the same time, we also hooked up a Plug-In Mains Power & Energy Monitor to allow us to monitor the total power draw from the system.

While this is not giving us definitive power consumption figures for the video card that is installed, we can measure the change in power consumption as a result of overclocking, and thus estimate how close the Radeon X800 XL is to the limits of the PCI-Express, or at least put some figures in to the melting pot to allow us to establish just how far the X800 XL could be capable of clocking without an additional power connector.