Plextor recently came out with the M5M SSDs, which are mSATA versions of the popular M5 Pro SSDs. It's Plextor's first entry into a small but growing niche segment. It's a bit surprising actually that so few manufacturers have released mSATA SSDs, since the small SSDs are a great way of speeding up your laptop.
Most laptops that came out last year feature an mSATA connector in addition to the standard 2.5-inch hard disk compartment. That way you can have a start-up SSD for your most important software, and a larger conventional hard disk for storage. In some ultra-thin Ultrabooks it's even the only available storage, so if you want to upgrade then an mSATA model is your only option.
Like their M5 Pro counterpart, the Plextor M5M SSDs are based on the latest generation Marvell controller, the Marvell 88SS9187, and it also features 19nm ToggleFlash memory from Toshiba.
The M5M comes in three sizes: 64 GB, 128 GB and 256 GB. We tested the 128 GB model.
According to Plextor, the 128 GB model has read speeds of up to 540 MB/s and write speeds up to 320 MB/s. The write speed is 20 MB/s less than what's specified for the M5 Pro 128 GB. It's not strange that the M5M is slower than the M5 Pro, since the smaller mSATA module only fits four flash chips compared to the eight on the M5 Pro. The controller therefore can't access as much flash memory at the same time.
The model we tested has a 256 MB buffer. The M5M 256 GB is supposed to have a write speed of 430 MB/s, while the 64 GB model is limited to 160 MB/s according to Plextor. Here are the exact specifications: