Is SATA bus speed unique for each device despite advertised connection speed?

Question

I'm trying to determine what is the maximum supported SATA version on my laptop. My laptop has: one mSATA SSD, one HD, one Optical Drive.

Using HwInfo, I see:

- Bus\Intel Panther Point-M PCH - SATA AHCI Controller:

  [SATA Host Controller]
  Interface Speed Supported:    Gen3 6.0 Gbps

So It seems that I have a SATA III controller; but then:

[SATA Port#0] (this should be the HD)
  Port Status:  Device Present, Phy communication established
  Current Interface Speed:  Gen2 3.0 Gbps

[SATA Port#1] (this should be the SSD)
  Port Status:  Device Present, Phy communication established
  Current Interface Speed:  Gen3 6.0 Gbps

[SATA Port#2] (this should be the Optical Drive)
  Port Status:  Device Present, Phy communication established
  Current Interface Speed:  Gen1 1.5 Gbps

So it seems that the HD has a SATA II. In fact under drives the HD shows as:

[General Information]
  Drive Controller: Serial ATA 3Gb/s @ 3Gb/s
  Drive Model:  WDC WD10JPVT-75A1YT0
  Drive Capacity:   953,869 MBytes (1000 GB)
  Drive Capacity [MB]:  953869
  Media Rotation Rate:  5400 RPM
  ATA Major Version Supported:  ATA/ATAPI-5, ATA/ATAPI-6, ATA/ATAPI-7, ATA8-ACS
  ATA Transport Version Supported:  SATA 3.0 

So what's the truth? My best guess is that the laptop has a unique SATA III controller, and the SSD is SATA III so maximum speed, the HD is SATA II so lower speed, the Optical Drive is SATA I so lowest speed.

If I replace the HD with a new SATA III SSD, will it perform as at SATA III or SATA II speed?

Answer 1

SATA Controller is a piece of hardware that takes care of communication between SATA Devices and System and one of requirements in specification is backward compatibility. This means that the SATA controller will work with all SATA devices regardless which generation of SATA interface the device has. Also most of optical drives are SATA I - no need for more.

From the HWInfo bits you pasted it seems that the SATA controller you have is Gen3 (6.0 Gbps). Thus it will work with all previous versions. ANd this also answers your question about swapping HD for SSD - it will be SATA III, provided the SSD will be SATA III compatible.