PC World – December 2015

REVIEWS
& RATINGS
Head to head
We took six M.2 SSD drives for a spin. The state of the art was
represented by these drives:
The $240, 256GB Samsung SM951 PCIe (AHCI)
The $240, 256GB Samsung SM951 PCIe (NVMe)
•
The $499, 480GB Kingston HyperX Predator PCIe (AHCI)
We also ran a last-generation $200, 256GB Samsung XP941
PCIe (AHCI) through its paces.
Also included are two SATA M.2 drives:
An older $300, 320GB Intel 530
•
A newer $99, 256GB Samsung EVO SATA drive
To be perfectly honest, we included SATA drives only to show you the
enormous performance gains offered by PCIe. Sneaky, eh?
Lastly, there was the aging $220 Plextor M6e, the first M.2 PCIe
(AHCI) drive we ever tested. It’s included to show just how far things
have come in a little over a year.
You may have noticed the parentheses indicating whether the PCIe
drives were AHCI (Advanced Host Controller Interface) or NVMe (Non-
Volatile Memory express). AHCI is basically the SATA protocol
implemented over PCIe (or any bus really), while NVMe (go.pcworld.
com/nvme) is a new communications protocol designed from the
ground up for non-volatile storage. AHCI over PCIe removes the
600MBps bandwidth limit, but NVMe offers some advantages for
multi-threaded operations, as you’ll see in the 4K queued test results
on page 71.
The only issue with NVMe is that your system must support booting
from it. All the motherboards I’ve seen that offer a PCIe-enabled M.2
slot allow booting from NVMe, but if you’re adding M.2 to your desktop
via a PCIe expansion card, you may need to go AHCI. Any motherboard
of relatively recent vintage should support booting from AHCI.
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