How can I enable 4way bank interleave?

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How can I enable 4way bank interleave on my Gigabyte K8N Pro-Sli motherboard? SiSoftSandra reports my G.Skill 1GB 4800 ram running on 2way bank interleave. I would like to see what performance I can gain by setting it to 4way, but can't find the setting anywhere in the bios? Even after pressing CTRL+F1 to enable hidden settings.

Can anyone help?

 

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It would appear that some motherboards have it, some don't?

There has to be someone out there who can answer

 

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I honestly cant find anything about this using google... can someone please help?