PCI-SIG-nificant Changes Brewing in Mobile and Small form Factor Designs



Of five significant PCI Express announcements made at this week’s PCI-SIG Developers Conference, two are aimed at mobile embedded. It’s about time.

The big news from the PCI-SIG is speed. From PCI to PCI Express to Gen3 speeds, the PCI-SIG is an industry consortium that lets no grass grow for long. As the embedded, enterprise and server industries roll out PCIe Gen3 and 40G/100G Ethernet, the PCI-SIG and its key constituents like Cadence, Synopsis, LeCroy and others are readying for another speed doubling to 16 GT/s (giga transfers/second) by 2015.

The PCIe 4.0 next step would likely become known as “Gen4” and it evolves bandwidth to 16Gb/s or a whopping 64 GB/s (big “B”) total lane bandwidth in x16 width. The PCIe 4.0 Rev 0.5 specification will be available Q1 2014 with Rev 0.9 targeted for Q1 2015.

Yet as “SIG-nificant” as this Gen4 announcement is, PCI-SIG president Al Yanes said it’s only one of five major news items.

Five PCI-SIG announcements at this week’s Developers Conference
The other announcements include: a PCIe 3.1 specification that consolidates a series of ECNs in the areas of power, performance and functionality; PCIe Outside the Box which uses a 1 – 3 meter “really cheap” copper cable called PCIe OCuLink with an 8G bit rate; plus two embedded and mobile announcements that I’m particularly enthused about. See Table 1 for a snapshot.

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Table 1: There were five major announcements made by the PCI-SIG at June’s Developers Conference.
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Figure 1: The PCI-SIG’s impending M.2 form factor is designed for mobile embedded ultrabooks, tablets, and possibly smartphones. The card will have a scalable PCIe interface and is designed for Wi-Fi, Bluetooth, cellular, SSD and more. (Courtesy: PCI-SIG.)

New M.2 Specification
One of two announcements for the mobile and embedded spaces, the new M.2 specification is a small, embedded form factor designed to replace the previous “Mini PCI” in Mini Card and Half Mini Card sizes (Figure 1). The newer, as-yet-publicly-unreleased M.2 card specification will detail a board that’s smaller in size and volume, but is intended to provide scalable PCIe performance to allow designers to tune SWaP and I/O requirements. PCI-SIG marketing workgroup chair Ramin Neshati told me that M.2 is part of the PCI-SIG’s deliberate focus on mobile in a fundamentally changing market.

The scalable M.2 card is designed as an I/O plug in for Bluetooth, Wi-Fi, WAN/cellular, SSD and other connectivity in platforms including ultrabook, tablet, and “maybe even smartphone,” said Neshati. At Rev 0.7 now, the Rev 0.9 spec will be released soon and the final (Rev 1.0?) spec will become public by Q4 2013.

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Figure 2: The Mobile PCI Express (M-PCIe) specification targets mobile embedded devices like smartphones to provide high-speed, on-board PCIe connectivity. (Courtesy: PCI-SIG.)
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Figure 3: M-PCIe by the PCI-SIG can be used in multiple high speed paths in a smartphone mobile device. (Courtesy: PCI-SIG and MIPI Alliance.)

Mobile PCIe (M-PCIe)
The momentum in mobile and interest in a PCIe on-board interconnect lead the PCI-SIG to work with the MIPI Alliance and create Mobile PCI Express: M-PCIe. The specification is now available to PCI-SIG members and creates an “adapted PCIe architecture” bridge between regular PCIe and MIPI M-PHY (Figure 2).

Using the MIPI M-PHY physical layer allows smartphone and mobile designers to stick with one consistent user interface across multiple platforms, including already-existing OS drivers. PCIe support is “baked into Windows, iOS, Android,” and others, says PCI-SIG’s Neshati.  PCI Express also has a major advantage when it comes to interoperability testing, which runs from the protocol stack all the way down to the electrical interfaces. Taken collectively, PCIe brings huge functionality and compliance benefits to the mobile space.

M-PCIe supports MIPI’s Gear 1 (1.25-1.45 Gbps), Gear 2 (2.5-2.9 Gbps) and Gear 3 (5.0-5.8 Gbps) speeds. As well, the M-PCIe spec provides power optimization for short channel mobile platforms, primarily aimed at WWAN front end radios, modem IP blocks, and possibly replacing MIPI’s own universal file storage UFS mass storage interface (administered by JEDEC) as depicted in Figure 3.

PCI Express Ready for More
More information on these five announcements will be rolling out soon. But it’s clear that the PCI-SIG sees mobile and embedded as the next target areas for PCI Express in the post-PC era. Yet the organization is wisely not abandoning the PCI Express standard’s bread and butter in high-end/high-performance servers and systems.


ciufo_chrisChris A. Ciufo is editor-in-chief for embedded content at Extension Media, which includes the EECatalog print and digital publications and website, Embedded Intel® Solutions, and other related blogs and embedded channels. He has 29 years of embedded technology experience, and has degrees in electrical engineering, and in materials science, emphasizing solid state physics. He can be reached at cciufo@extensionmedia.com.

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