VIA has issued a warning
of problems with chipset support for hard drives using the Serial ATA II standard. Seemingly, VIA's VT8237 and VT8237R chipsets don't provide forward compatibility for Serial ATA II. As hard drive makers are increasingly moving towards this type, this could be a problem for customers who bought these chipsets and might be seeking to do a hard drive upgrade. To combat these issues, VIA is getting ready to release VT8237R Plus, which will solve the problem.
Western Digital and Samsung are already shipping these Serial ATA II devices, while Seagate and Maxtor will start shipping them during this quarter.
If you connect S-ATA II drives to an old VIA chipset which includes the VT8237, VT8237R, VT6420 and VT6421L, the devices won't be detected.