What RAID/HBA card were you using and what firmware version is on your expander? I'm starting to wonder if there are different PCB revisions of the expander that might have something to do with this.
Tried all of those things with no luck. With the drives connected directly to the expander with a breakout cable, they're still negotiating at 1.5. Anything connected to the RAID/HBA cards directly or through the backplane negotiates at the spec of the drive (3 and 6).
Long time stalker, first time poster.
I've seen a lot of mention in this thread about these expanders having issues sometimes where they negotiate at 1.5Gb/s even with the newer firmware versions.
I just got a new one of these cards off eBay, and the negotiated speed is 1.5Gb/s regardless...