Look at: chart on page in link - I removed the other pictures, chart attached below
http://arstechnica.com/gadgets/2015/02/understanding-m-2-the-interface-that-will-speed-up-your-next-ssd/ Gear & Gadgets / Product News & Reviews Understanding M.2, the interface that will speed up your next SSD
It's a versatile standard, but there's a lot to know.by
Andrew Cunningham - Feb 8, 2015 5:02pm EST
Enlarge / Four M.2 cards, from left to right: An A- and E-keyed Wi-Fi card, two B- and M-keyed SSDs, and an M-keyed SSD.
Andrew Cunningham
Most of this information originally appeared in our review of
Intel's Broadwell NUC. Since it's of general interest to anyone buying or building a PC, we're posting this slightly edited and expanded version as a separate piece to make it easier to find and reference.
Most solid-state drives released within the last year or so have been too fast for the bus they're connected to. The 6Gbps SATA III spec was finalized in the days when rotational hard drives still ruled and SSDs were rare, ludicrously expensive, and relatively unreliable.
There are a couple of different standards that have been created to solve this problem, and they both solve it in the same basic way. One,
SATA Express, uses the same physical connector as older SATA drives but uses PCI Express lanes rather than the SATA bus to boost storage speeds. The other, which will be more common in space-constrained mini-desktops, all-in-ones, and Ultrabooks, is called M.2 (previously NGFF, for "Next-Generation Form Factor").
M.2 is interesting not just because it can speed up storage with PCI Express lanes, but because it can use a whole bunch of different buses too; it stands to replace both mSATA and mini PCI Express, two older standards that have been used for SSDs and Wi-Fi cards in laptops for a while now. Intel's new Broadwell CPUs and their chipsets include native support for M.2 and PCI Express boot drivers—neither PCIe-connected storage (
hi Apple) nor
the M.2 connector itself are new, but beginning with Broadwell systems each of those two things will become much more common.
Let's start with the physical connector and the things that connect to it. There's a lot to unpack, starting with the fact that there's more than one kind of M.2 connector, more than one type of interface that can be used with M.2, and more than one kind of M.2 card.
Laptops will benefit more from these new chipsets than desktops will.
Pictured at the top of this article are four different M.2 cards. The one on the left is a combo Wi-Fi and Bluetooth card. The next one to the right is a Sandisk SSD that uses the SATA bus. The next one is an Intel SSD that also uses SATA. The one on the right is a Samsung SSD that can use up to four PCI Express lanes.
Pay attention to two things as you compare and contrast these cards. First, the physical connector on each card is different; each card has different cutouts in the bottom and exposes different pins. Second, the cards are of different lengths and widths. All of this is accounted for in the M.2 spec (
PDF).
The different connectors signify different M.2 "module keys." Each key exposes a different set of interfaces to each card—M.2 can connect directly to the PCI Express bus, but different pins can be used to connect to the USB 2.0 and 3.0 buses, SATA III, DisplayPort, and a variety of other less-prevalent storage buses. Cards with one notch at the bottom are keyed for one specific kind of connector. Cards with two notches can be used in two different kinds of connectors.
Enlarge / Two M.2 slots on the motherboard of the HP Stream Mini. The left one is E-keyed and used for the Wi-Fi card. The right one is B-keyed and used for the SSD.
Andrew Cunningham
Above is a picture of two M.2 slots on the motherboard of an HP Stream Mini. The slot on the left uses module key E, and the one on the right uses module key B. The Wi-Fi card is keyed for slots A and E, so it fits in the left slot with no problems. The Intel SSD is keyed for slots B and M, so it fits in the right slot. The Samsung SSD is keyed for slot M, so it won't fit in either of the Stream's slots.
KeyCard measurementsInterfacesCommon usesA1630, 2230, 3030PCIe x2, USB 2.0, I2C, DisplayPort x4Wi-Fi/Bluetooth, cellular cardsB3042, 2230, 2242, 2260, 2280, 22110PCIe x2, SATA, USB 2.0, USB 3.0, audio, PCM, IUM, SSIC, I2CSATA and PCIe x2 SSDsE1630, 2230, 3030PCIe x2, USB 2.0, I2C, SDIO, UART, PCMWi-Fi/Bluetooth, cellular cardsM2242, 2260, 2280, 22110PCIe x4, SATAPCIe x4 SSDs
The table above lays out the keys in common use today—there are others, mostly placeholders to be called into service as newer buses and interfaces are introduced.
Note the four- or five-digit numbers paired with each slot. These are actually codes to refer to the physical dimensions of each card; the first two digits specify the width in millimeters and the second two or three digits specify the length. Our Wi-Fi module is 16mm wide and 30mm long, or 1630. Two of our SSDs are 22mm wide and 80mm long, or 2280. The other SSD is 22mm wide and 42mm long, or 2242. All motherboard slots are 22mm in width, even the ones attached to 30mm-wide cards.
All current keys can give cards access to two PCI Express lanes, but otherwise interface compatibility is all over the place—so far, it's been pretty easy to guess what kind of peripheral you're dealing with based on the key it uses. Wi-Fi and WWAN cards tend to use keys A and/or E, since they only need the PCI Express or USB 2.0 buses and only need 30mm in length to fit all their key components. SATA SSDs and SSDs that use two PCI Express lanes tend to use keys B and M to maximize compatibility, since both connectors can deliver both SATA III and two PCIe lanes. The very fastest SSDs tend to be M-keyed since it's the only one that delivers four PCIe lanes.
post edited by Cool GTX - 2015/12/01 13:25:45
Attached Image(s)
