On Thu, Jul 23, 2015 at 04:11:11PM -0400, Bryan J Smith wrote: > You mean you've been looking at mainboards. ;)
Sure. > BTW, Asus is a poor example of an OEM, because most of their products > are now fabbed two (2), different, external ODMs (ECS and Foxconn).** > > Mainboards are a crapshoot of non-standards, and worse than notebooks. > > I.e., even most Tier-2 notebooks, and even some Tier-1 brands/models > (e.g., Alienware, etc...) use the same ODM (Clevo). > > > 10 variants do PCIe and SATA, > > 5 do only PCIe (one of which is PCIe x4). > > If you have _true_ PCIe x4 (and SATA), then it has to be a "M" card > and socket. Although there is soft logic to prevent most issues, most > B+M dual-types are actually only PCIe x2 (plus SATA) for a reason. > They avoid the other traces that B offers for USB, audio, etc... > > But mainboards are a crapshoot, and you'll get a lot of non-standards. > > > Quite a few M.2 cards are SATA only > > Nearly all are. That's because the first "native" PCIe NAND > controllers were only fabbed in the last few months, and still being > "sampled." > > The few M.2 PCIe cards out are using a yesteryear, external PCIe 2.0 > bridge chip fabbed at old 65-90nm technologies. They were not > designed for the type of throughput NAND is capable of. > > I.e., Most high-speed PCIe devices have their PCIe controller built > on-package, if not on-die with the ASIC. > > E.g., Mellanox fabs most of the "unified" ASICs used in > network-controller NICs/HBAs (Eth, FC, IB) > > > and hence don't work on such a board that has one PCIe > > of course. > > There have been a lot of issues with mainboards doing stupid things to > the point I won't trust the first generation. > > I.e., I'm going to stick with a PCIe adapter card that to adapt a M.2 > B/M type card so it does both PCIe x4 (or x1 if in a x1) and SATA. Well certainly so far it looks like early onboard designs are going to be a compatibility mess. > > Supposedly with the latest UEFI version and a 'hyper kit' > > adapter, those PCIe enabled M.2 slots on the asus board > > also natively run NVMe with a mini SAS connector. > > You mean SATA-Express? > It's not really related to M.2 ... at all. No they really do seem to be doing NVMe by using the PCIe link of the M.2 slot. > I.e., M.2 (and PCIe "expansion cards") already have PCIe traces. > The SATA-Express is so you can "cable in" the PCIe traces. ;) > > E.g., so 2.5" form-factor NAND devices can use PCIe. Yes they are aiming for the 2.5" NVMe drives, like the intel 750 (SSDPE2MW400G4R5 for example), which is listed as a 2.5" drive with a PCIe 3.0 x4 interface. Sure looks like a SATA connector of course. Of course given the same size intel 750 can be bought for about the same price as a PCIe 3.0 x4 card to plug into a slot instead, for a desktop or server that may well be the better way to go and avoid adapters and weird cables and such. -- Len Sorensen _______________________________________________ lpi-examdev mailing list lpi-examdev@lpi.org http://list.lpi.org/cgi-bin/mailman/listinfo/lpi-examdev
