The device numbers are given through the hardware. They're the order in which your system detected them. if they're physical cards, switching them around in the PCI/PCIe slots will change their numbers.

But otherwise yes, the ignore device option in cc_config.xml will do it. Whether or not this must be an ATI device in your case is something we cannot advise on, since you have your computers hidden and didn't say anything about what GPUs you have in your system.

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