MacBook Pro bus speed velocity (Hard-Drive, CD/DVD Drive, Card Reader)

According to the MacTracker app, all three models have the main drive bays use SATA III (6Gbps) controllers. The optical drive bays for the Late 2011+ show as 6Gbps as well. The Early 2011 model has MacTracker showing 3Gbps or 6Gbps for the Optical drive bay. If the optical drive bay is 3Gbs then you may want to use a 3G (aka SATA II only) SSD such as the OWC Mercury Electra unless there is a system firmware update which opens up the optical drive controller to 6Gbs.

You definitely want to replace the internal hard drive cable on the 13" (mid-2012) model since the internal cables are notorious for failing especially with an SSD installed. You may need to do the same on the others as well although I have not needed to do so yet.

Choose your SSDs wisely as not all manufacturers provide OS independent firmware updaters. Some Samsung SSDs are known to have compatibility issues, but I'm not sure which exact Samsung models have the issues.

And how can I check if the drive bay is 3Gbps or 6Gbps?

>(option key) System info>Hardware>SATA/SATA Express

For Drive Bay:

The SDcard reader on 2011 is USB2, on the mid 2012 USB3

BOXERBOSS wrote:

Mine shows exactly like your print-screen, so it is 6Gbps for hard drive and 6Gbps for drive bay, isn't it?

At Card reader section, show this in the screenshot attached (2.5 GT/s is the speed?)

That stands for Gigatransfers per second. 2.5 GT/sec is a single PCIe lane and ideally can transfer up to 4 Gbit/sec after overhead. When you see SATA speeds, that just the raw link speed and doesn't account for protocol overhead.

https://www.edn.com/electronics-news/4380071/What-does-GT-s-mean-anyway-

Pretty much every SATA-III SSD these days is rated at 560/530 Mbit/sec read/write.

BOXERBOSS wrote:

Whats the reason for the internal cables failing especially with an SSD installed ?

Internal SATA cables are actually not cables but flexible circuit boards, usually mylar, with printed circuit traces taking the place of wires. This type of cable can experience cracks in traces due to aging, heat, vibration, impact and abrasion. They can be damaged quite easily if the unit is mishandled during assembly or re-assembly.

In the case of an intermittent generic failure, the electrical continuity of a cracked trace on both sides of the crack is very often a function of the temperature of the unit at the point where the crack exists. As a unit heats up, it expands, and as it expands, the crack widens, eventually forcing a complete electrical separation to exist on both sides of the crack, hence a failure. As it cools down, electrical contact may once again be restored.

SSD= faster I/O speed= more heat in the trace.

Addendum— If the HDD/SSD is removable it has always been the go to way to diagnose by putting it in an external enclosure bypassing the internal SATA cable.

added electric tape for padding of the SATA cable.