With the first Surface Books shipping, we’re getting a better picture of what Microsoft’s new convertible looks like. According to the latest reports, Microsoft chose to use a slower TLC SSD instead of a caster MLC model. While mostly offering a superb SSD performance, the TLC-based Samsung PM951 falls short with its write speeds.
For the 128GB model, the Surface Book clocks a meagre 150MB/s and the 256GB model only manages about 280MB/s. Unlike the popular SM951 which uses MLC NAND, the PM951 sports 19nm TLC which is inherently slower. Due to this, the PM951 has write speeds similar to 2011 and 2012 SSDs from 3-4 years ago like the Samsung 830 and 840. In fact, the 150MB/s speed for the 128GB is pretty much on par with HDDs which is telling.
While TLC is part of the issue, the bigger problem is the lack of NAND parallelism. Each NAND die has speed limits and SSDs gain their superb speeds by writing to many NAND dies simultaneously. As NAND lithography shrinks and denser methods like TLC are used, fewer and fewer NAND dies will be needed for a certain capacity.This all happens before we even consider other limitations like M.2 which limits the number of NAND dies as well.
There are benefits to using TLC and lower lithographies, chiefly the ability to hit a higher capacity at lower cost. In order to compensate the decreased NAND parallelism, we must turn to things like 3D-VNAND and NVME, which can raise costs. On the other hand, the prices OEMs charge for storage should be more than enough to ensure only top end SSDs make it into premium products.
For the Surface Book, the increase to higher storage capacities is pretty insane. For an increase of 768GB of storage, Microsoft charges about $1000 which is well above what Samsung charges. For an increase of a more modest 256GB, there is a $500 price bump. These cost increases would more than cover going to faster SSDs like the SM951 or PM987. Given these prices and the premium nature of the Surface Book, it seems natural that Microsoft would have made sure storage is up to par. Hopefully, Microsoft and other OEMs will take note of this with their future products.
