As existing standards evolve, there's more of a tendency to drag along support for the legacy features found in earlier versions. Backwards compatibility has always been an admirable goal. But when a completely new standard arrives on the scene, the age-old expression is often true, "out with the old, in with the new." Even though the technology has already been developed, continuing to support older functionality does carry a burden. It might take up some precious real estate and add a few cents to the BOM. But even if doesn't, one has to at least factor in the time and costs associated with testing it. That's why the architects of the new Qseven Computer-on-Module (COM) standard decided to part with some legacy "baggage."
If you're not already familiar with it, Qseven's name stems from its Quadratic (i.e. square) 7 x 7 cm (2.75 x 2.75-inch) format. Qseven targets low power, ultra-portable platforms, including handheld devices deploying 45nm processors such as Intel® Atom. Starting off my list of "what's missing," compared with most previous COM standards Qseven drops an expensive board-to-board connector, instead utilizing the cost effective "golden finger" connector borrowed from the MXM (Mobile PCI Express Module) graphics interconnect standard used in laptops. Curiously enough, I bumped into at least one manufacturer's COM that has adopted not only the MXM connector but conforms to the full MXM format. It doesn't have an Intel processor, though.
Other things you'll find missing are the fan and the power cord. Actually the standard doesn't prohibit either but it does specify 5V power with maximum dissipation of 12 watts. The point is you probably won't need a fan and Qseven modules will likely find their way into many battery powered devices, for which the spec. defines battery management guidelines. For reference, note that the Intel® Atom Z5xx processor series combined with the US15W System Controller Hub (SCH) chipset has a sub 5 watt TDP.
As for reduction in footprint, critics will argue that the existing 5.5 cm x 8.4 cm nanoETXexpress module is already a bit smaller, so Qseven doesn't appear to offer any new advantage purely on the basis of size.
Qseven footprint vs. nanoETXexpress
Deleting some cost and fans and power cords are all good things. Is there anything left out of Qseven that systems designers will miss? The founding fathers of Qseven decided to support only "the feature set of current and future mobile chipset/CPU combinations." Therefore older interfaces, such as Parallel IDE and PCI Bus, have been deliberately omitted.
On the "in with the new" side of the equation, Qseven incorporates modern fast serial differential interfaces, including PCI Express and Serial ATA; graphics panel and digital media specs such as DisplayPort and HDMI; and claims to be the first COM standard to support SDIO which, among other benefits, will enable cheaper bulk memory than CompactFlash.
Legacy features not supported
Modern interfaces added
Click here to check out a short video presenting the highlights of Qseven, or visit http://www.qseven-standard.org/ for the complete specifications and for list of member companies in the standards consortium, many of which are members of the Intel® Embedded and Communications Alliance. You'll also find within our community several available products in the Qseven form factor featuring Intel® Atom processors.
As a future-looking COM standard for low power, ultra-portable devices, do you see anything missing from Qseven?
J. Felix McNulty
Intel® Embedded Design Center Community