Yes, SSDs are not officially supported on the SAS 6/iR.
I happen to be running a similar configuration on my home desktop system. I hadn't even noticed that my 840 EVO had negotiated to 1.5.
I booted into the SAS 6 controller BIOS and indeed the 840 negotiated to 1.5. I am running my OS on the 250GB 840 EVO and have 2x1TB SATA drives in a RAID 0 for data. The SATA drives are at 3.0.
I installed the latest Samsung Magician software: http://www.samsung.com/global/business/semiconductor/samsungssd/downloads.html and used it to update the EVO to the latest firmware. I restarted and booted back into the controller BIOS with no change. It was still negotiating to 1.5.
I then stole an interposer from one of my 2950 servers and attached it to the 840 EVO. I booted back into the controller BIOS and it is now negotiating to 3.0, so it would appear that an interposer will allow it to negotiate link speed properly.
Dell EMC, Enterprise Engineer
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