If "Negotiated Link Speed" is lower than "Link Speed"..?

lip5016

macrumors regular
Original poster
Jul 11, 2014
174
26
From my "About This Mac":

Intel 6 Series Chipset:

Vendor: Intel
Product: 6 Series Chipset
Link Speed: 6 Gigabit
Negotiated Link Speed: 3 Gigabit

Physical Interconnect: SATA
Description: AHCI Version 1.30 Supported

What does "Negotiated Link Speed" mean?
Does that mean that this drive listed above will only run at 3 Gigabit, and not the full 6 Gigabit?
 

prisstratton

macrumors 6502a
Dec 20, 2011
534
121
Winnipeg, Manitoba, Canada
From my "About This Mac":

Intel 6 Series Chipset:

Vendor: Intel
Product: 6 Series Chipset
Link Speed: 6 Gigabit
Negotiated Link Speed: 3 Gigabit

Physical Interconnect: SATA
Description: AHCI Version 1.30 Supported

What does "Negotiated Link Speed" mean?
Does that mean that this drive listed above will only run at 3 Gigabit, and not the full 6 Gigabit?
Seeing as you listed 2 x SSD, I am guessing that you put one in the opti-bay and this is the one you are referring to. If that is the case then your model MBP does not support (reliably.....according to OWC) 6 Gigabit in that location.
 

simonsi

macrumors 601
Jan 3, 2014
4,850
734
Auckland
From my "About This Mac":

Intel 6 Series Chipset:

Vendor: Intel
Product: 6 Series Chipset
Link Speed: 6 Gigabit
Negotiated Link Speed: 3 Gigabit

Physical Interconnect: SATA
Description: AHCI Version 1.30 Supported

What does "Negotiated Link Speed" mean?
Does that mean that this drive listed above will only run at 3 Gigabit, and not the full 6 Gigabit?
Correct. You are connected at 3G even though the link controller chip supports 6G.
 
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lip5016

macrumors regular
Original poster
Jul 11, 2014
174
26
Correct. You are connected at 3G even though the link controller chip supports 6G.
Really weird. Somehow after installing OSX on the 2nd disk, it became 6G across the board for everything.. go figure lol
 

simonsi

macrumors 601
Jan 3, 2014
4,850
734
Auckland
Really weird. Somehow after installing OSX on the 2nd disk, it became 6G across the board for everything.. go figure lol
There are various conditions that will cause the link speed to be renegotiated (power off/on is the obvious one), it will likely also periodically attempt to renegotiate higher if seeing no transmission errors across the interface, as well as negotiate down if it does see errors. "Periodically" could be data-volume based so if you moved 20GB (say) installing the OS then that may have caused an in-flight renegotiation of the link speed.

If it continues to fluctuate 3G-6G-3G then it might be worth replacing the interface cable to see if that improves the link quality. Equally if you can't tell in usage if the speed steps down, it may not be worth worrying about :cool:
 

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