Asrock U.2 sff-8639 adapter?

There are two main types of M.2 SSDs, standard SATA and the PCIe types, for a lack of better terms. The interface or "key" on those two types are different, but normally fit and work in an M.2 slot/port/interface.

The SATA M.2 SSDs are the same as a standard 2.5" SATA SSD regarding drivers, and are detected by the Intel IRST driver and Windows UI just like standard SSDs.

The PCIe SSDs like the Samsung XP941 and SM951 have their own SATA controller on the drive itself, and use the standard Windows AHCI driver, msahci or storahci.

When using these SSDs you'll get a Device Manage entry under IDE ATA/ATAPI controllers, Standard SATA AHCI Controller. They also need the Intel UEFI compatible SATA Option ROM that is part of the UEFI/BIOS image. Plus a UEFI/BIOS update is needed before they can be bootable. These SSDs are not recognized by the IRST Windows UI, and in fact I cannot get the IRST Windows UI to install on my Z97 Extreme6 board when my SM951 is the OS drive. The IRST driver installs fine.

The main reason the PCIe M.2 SSDs are popular in desktop PCs is because they perform better (more in benchmarks than actual use IMO) than SATA SSDs. Plus they are a clean, simple installation, no cables to deal with.



Regarding Skylake information, don't forget NDA...

Thanks odiebugs, I was agreeing with your earlier posts in this thread, and I still do.

Some owners of the Intel 750 NVMe SSD have reported slower booting times compared with their SATA III SSDs. The Microsoft NVMe driver seems to not work well with the Samsung NVMe version of the SM951 (or whatever it is called now.) Intel supplies an NVMe driver for the 750.

I considered an Intel 750, but got a Samsung SM951 instead. IMO, NVMe needs to get sorted out for PC use, so I'll wait a while.

I don't get the SATA Express support on mobos, not one SE SSD exists.

Samsung just announced new 2TB SSDs, not sure about the prices.

If anyone is still complaining about SSD prices, and don't have one, they are missing out on the best upgrade they could do for their PC.

NVMe is really the next evolution of NCQ provided by AHCI, with other important enhancements.

Instead of one 32 IO command queue, NVMe provides up to 64K IO command Submission Queues, with each queue containing up to 64K IO commands. NVMe also provides multiple IO Completion Queues, paired with a Submission Queue, that contains the data requested.

Completion queues can be associated with CPU cores, so the data can be processed in parallel.

In typical PC usage when using a SSD, the AHCI NCQ queue depth rarely if ever reaches four IO commands, since SSDs are so fast at providing data. So the new IO request and data queuing capability won't be used much by most of us.

The Submission and Completion Queues are controlled by software (NVMe driver) which is not active during OS booting (or at least some of it) so does not make booting faster.

The NVMe enhancement that will benefit PC users is its reduced processing overhead for random, small IO requests. That kind of IO is slowest in any storage device.

Non-volatile storage IO is the main bottleneck in all computers, hopefully NVMe will benefit PC users and enterprise usage.

sparx wrote: I suspect Sata Express will die before even someone presents a drive where its useable.  Sure, U.2 is still a bit early. Not really a conformed standard. The connectivity to motherboards is a bit of a mess. But the drives are here to stay. Or atleast NVMe. It just needs to become better priced. But the Intel 750 series are a good start! And motherboard manufactorers need to start placing an SFF-8643 (with PCIe) on the boards itself. Maybe for Skylake we will see it.

Sata -E is dead.

I suspect Sata Express will die before even someone presents a drive where its useable.