M.2. Please Just Standardize
To complicate vastly complicated matters, a third type of drive was soon to arrive on the scene, M2 PCI-E Gen 2 x4.
The fleetest of all so far, these drives again were wholly dependant on the PCI-E bus for their data exchanges but used four lanes instead of two, doubling the available bandwidth and raising potential speeds to 20 gigabits per second. They sported a slightly different connector with only one notch, the M key present, the B key being replaced with two contacts, allowing access to the additional PCI-E lanes.
To summarize:
M.2 Sata = M and B Keys
M.2 PCi-E Gen 2 x2 = M and B Keys
M.2 PCI-E Gen 2 x4 = Only M Key.
As if this weren’t enough to vigorously scramble the poor customer’s grey matter, manufacturers frequently chose to electrically wire the sockets on their products to operate with just one of these three devices. Sometimes, it would be Sata only, as was the case with the adapter below:
This meant such drives as the Plextor M6e (a PCI-E 2.0 x2 based M.2 drive) would not be recognized but the Toshiba THNSNH512GDNT THNSNH512GDNT (a SATA based M.2 drive) were detected, despite both being physically compatible with the slots.
In other instances, the reverse was true.
The card above could be paired up with PCI-E 2.0 M.2 drives such as the Samsung XP941 and the Plextor but offered no support for SATA propelled M.2s like Toshiba.
In the case of M.2 Sata modules, the M key was only present to enable their installation in PCI-E M.2 sockets, assuming, of course, these had been connected to the motherboard’s SATA controller.
Numerous sites, including several hosted by e-tailers actively selling the product, claimed that it could only identify PCI-E modules with the B key removed and all four lanes accessible and that x2 devices incorporating both keys failed to function. In practice, this was utter nonsense, as was evidenced by the following insightful analysis on Custom Pc Review.
It’s one thing when bemusement reigns as a result of diverse experiences amongst consumers and reviewers but when manufacturers themselves appear incapable of divulging accurate specifications, what bloody hope is there?