I’m using USB 3.0 and I know there are no issues with BIOS or anything else because a different brand of ssd is scoring where these drives should be. I am testing with Crystal Disk Mark. On sequential read and write my scores are 241 read and 81 write. All other 6 parts of the test are 25 or lower. My other brand on sequential scores 336 read and 212 write. Plus it scores 173/125 on 8queues/8 threads and 155/128 on 32 queues/1 thread and 25/38 on 1queue/1 thread. My sandisk scores 10 to 13 at the highest on any of those parts of the test. Is this a bad unit? Here is a photo with different numbers but you get the point. I ran another test and took screenshots.
May be a faulty unit. How old is your Extreme?