so then why are there jumpers on some disks?
this is from wikipedia, about SATA:
"According to the hard drive manufacturer Maxtor, motherboard host controllers using the VIA and SIS chipsets VT8237, VT8237R, VT6420, VT6421L, SIS760, SIS964 found on the ECS 755-A2 which was manufactured in 2003, do not support SATA 3 Gbit/s drives. To address interoperability problems, the largest hard drive manufacturer Seagate/Maxtor have added a user-accessible jumper-switch known as the Force 150, to switch between 150 MB/s and 300 MB/s operation.[3] Users with a SATA 1.5 Gbit/s motherboard with one of the listed chipsets should either buy an ordinary SATA 1.5 Gbit/s hard disk, buy a SATA 3 Gbit/s hard disk with the user-accessible jumper, or buy a PCI or PCI-E card to add full SATA 3 Gbit/s capability and compatibility. Western Digital uses jumper setting called "OPT1 Enabled" to force 150 MB/s data transfer speed."