A system for processing subscriber line data signals uses a coprocessor to receive signals in a pre-determined order from a plurality of line interface cards. The coprocessor uses the pre-determined order to sort the data signals by tone and process all received signals on the same tone at the same time. Because all signals on a tone, or those on a tone with known crosstalk issues, are processed together, the signal improvement is better than prior art methods. When not used, the coprocessor may be replaced with a loop-back circuit to reduce cost when crosstalk is not a significant issue.