How to reduce the SATA link speed of drive in CentOS?

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http://serverfault.com – How do I make CentOS run SATA drives at 3Gb/s at boot? Background: I'm having an issue with a motherboard that claims to support 6Gb/s SATA transfer speeds, but when using 4 drives on it, in a software RAID 10 with heavy disk IO, some of the SATA links start throwing kernel errors, ie. ata1.00: failed command: WRITE FPDMA QUEUED. But it's a different drive each time, not always ata1, and running extended test on each disk individually produces no errors. When the errors occur, the Kernel/OS (CentOS 6.2) eventually resets the link several times, and when it continues to fail, then it changes (HowTos)