The SM951 story has developed since we first shucked a drive from a Lenovo X1 Carbon Gen 3 two months ago. Resellers are selling them at better-than-expected prices. Samsung also announced a new NVMe model appropriately called the SM951-NVMe. The company's 512GB SM951 offers attractive performance for its price, but many waiting for an even better value want information on the smaller capacities before jumping into the world of PCIe-based SSD performance.
If you read our first SM951 review, then you already know the drive we pulled from Lenovo's Ultrabook failed to reach Samsung's SM951 performance specification for sequential reads. At the time, we suspected that Lenovo was limiting the drive to conserve battery power. With more samples in our hands, we now know the issue is Lenovo-specific, and it doesn't affect drives sold by other vendors.
Today we're testing the 128 and 256GB versions of Samsung's SM951 next to the XP941, which officially surfaced in 2014. Back then, the XP941 was the only native PCIe SSD on the market. Marvell has since joined the fight with two native PCIe controllers that will also be represented in the benchmark charts today.