Backwards compatibility for SATA

To be absolutely sure, go to the websites of HDD manufacturers and look for exact details of how you can force their units to slow down to the older 1.5 Gb/s rate. I'm pretty sure that Seagate and WD both do this with a jumper placed on pins on the back edge of the drive. NOTE: these pins and jumpers are NOT anything like the Master and Slave systems on IDE drives - in fact, there is NO Master or Slave in SATA systems. The jumpers and pins on SATA drives are for other things. Other than forcing the slower original SATA speed, you should not change these jumpers unless you really know what you're doing.

As I understand it, other HDD makers like Hitachi had other methods for forcing the slower speed, like running a software utility to adjust a HDD board setting. Just make sure you know exactly how to do the job on exactly the drive you plan to buy. Then you'll have no trouble. In fact, at one time (maybe not now, I don't know) Seagate supplied their drives with the jumper in place to force the slower speed, and anyone who knew they had a SATA II controller was supposed to remove that jumper.

Ideally, SATA II drives connected to older SATA controllers are supposed to figure this all out and adjust themselves automatically. But sometimes this fails, and you need to set it manually. If you do that when necessary, I've never seen a report here that says the adjustment failed to solve the issue.