Early 2009 Mini w/ Samsung 840 EVO Speed Troubles

[RyanThaDude]

After finding out the issue with the Nvidia MCP79 chipset in my older Mini (Macmini3,1) with Sanforce SSDs, upon many recommendations on this site and elsewhere, I purchased a Samsung EVO 840 120GB. I replaced the drive, installed Mavericks and enabled TRIM, checked System Information, and sure enough, I'm seeing the ugly bug rear it's head with this drive!

NVidia MCP79 AHCI:

  Vendor:	NVidia
  Product:	MCP79 AHCI
  Link Speed:	3 Gigabit
  Negotiated Link Speed:	1.5 Gigabit
  Physical Interconnect:	SATA
  Description:	AHCI Version 1.20 Supported

Samsung SSD 840 EVO 120GB:

  Capacity:	120.03 GB (120,034,123,776 bytes)
  Model:	Samsung SSD 840 EVO 120GB               
  Revision:	EXT0BB6Q
  Serial Number:	S1D5NSBF241496B     
  Native Command Queuing:	Yes
  Queue Depth:	32
  Removable Media:	No
  Detachable Drive:	No
  BSD Name:	disk0
  Medium Type:	Solid State
  TRIM Support:	Yes
  Bay Name:	Lower
  Partition Map Type:	GPT (GUID Partition Table)
  S.M.A.R.T. status:	Verified

I tried an Intel 530 SSD for a while, but would only negotiate at a 1.5Gbps since it was a Sandforce SSD. But why am I seeing this on this 840 EVO? I don't get it! Everywhere I've read this SSD was the one to use! Both the Mini and SSD are up-to-date with firmware.

The drive is working, but if I can't get it to negotiate at 3Gbps, then I could've left my Intel SSD installed and saved the $80 and headache!

EDIT: I just want to add I've also reset the PRAM and SMC without success.

 

[RyanThaDude]

So it has come to this. I removed the SuperDrive out of the bay, and installed the SSD there. Replaced the original Hitachi 320GB drive back in the "lower" bay. Again, reset PRAM and SMC, then rebooted. System booted normally from the Samsung 840 EVO without issues and recognized the Hitachi. Checked system information again. Success, the SSD is 3gbps as it should be. However, the Hitachi remains at 1.5, despite being the actual original drive that came with the Mini.

 

[Mr. Retrofire]

...However, the Hitachi remains at 1.5, despite being the actual original drive that came with the Mini.

It is possible that your drive supports only SATA@1.5 GBit/s. This table lists some 1.5 GBit/s models:
http://www.hgst.com/tech/techlib.nsf/techdocs/c51a283f52498251862573fa005a3c98/$file/travelstar_5k320_ds.pdf