Set for ratification this year, QMC (VITA 93) is VITA’s next-generation small form factor Mezzanine (SFFm) standard that focuses on system expansion, while supporting existing embedded computing form factors. 

Designed to seamlessly integrate with current open standards, like VPX, SOSA, and VNX+, QMC addresses modern high-speed data processing needs through modularity and flexible I/O. We asked some VITA community members:

How will QMC impact system development moving forward, and what challenges will it help designers mitigate in rugged, high-speed data applications?

Matt Burns, Global Director, Technical Marketing, Samtec

Smaller. Faster. Denser.

Samtec uses this phrase to describe the continual evolution of high-performance, high-frequency copper, optical, and RF interconnects in Data Center, AI/ML, HPC, T&M, and other bleeding edge applications. That same evolution is taking place in rugged computing, embedded computing and related applications.

Existing rugged computing technologies like VPX have been available for some time. Existing I/O form factors - VITA 57, VITA 42//61/88, etc. - typically support data rates up to roughly PCIe 4.0 (16 Gbps) or even PCIe 5.0 (32 Gbps). However, the interconnects used in these form factors are performance limited as system form factors like VITA 90 VNX+ are getting smaller and legacy FMC/FMC+ and XMC/XMC+ expansions cards are just too big. 

VITA 93 QMC addresses all these technical design concerns and trends. VITA 93 QMC leverages the Samtec AcceleRate® HD ultra-dense slim body arrays which feature a 0.635 mm pitch, 5-16 mm stack heights, and a 5 mm wide profile. The connector also supports a path to PCIe 6.0 (64 Gbps PAM4). This is a necessity as embedded processors now offer native support for the latest PCIe protocols.

Of course, a connector by itself doesn't guarantee high-speed performance. However, the optimized SI design of the VITA 93 QMC connectors are known. This helps system designers choose the latest PCB laminates and implement the latest design rules of their current and future carrier cards. Additionally, the scalability, flexibility, and small size of the QMC form factors support many I/O uses case from data acquisition, fabric connectivity and GPIO. That is very powerful for implementing next-gen system topologies in rugged computing. 

Nino Addamo, Product Marketing Manager, Concurrent

Today’s system development process faces challenges, despite the performance and versatility of our processor products, designers typically rely on using XMC to add I/O which is difficult with limited space and rising power consumption.

Instead of using a single XMC for user I/O, the application of QMC would allow for much greater granularity as it is possible to fit multiple single QMC modules on a single 3U VPX host. Systems typically require a small number of multiple interfaces, for example two additional ethernet ports and one ARINC 429. In our current model this would require two XMCs each taking up a 3U VPX slot. QMC minimizes and simplifies this process by providing a single module format that suits system applications needing more than one interface type at low channel count.  This improves cost effectiveness and the Size, Weight and Power (SWaP) metric for systems.

Additionally, the core processing element of our products have significantly increased in size and power consumption. Components used in our 3U VPX products today, and potentially VITA 100 in the future, such as the CPU, FPGA and GPGPU take up a substantial part of the available board area. For example, Concurrent’s recently announced Kratos product utilizes a very large 20-core CPU which requires 145W, generating significant heat. Fitting an XMC directly above a processor like this is impractical, however it is viable to fit one or more single QMC around this type of processor allowing additional I/O within a single slot.

In summary, QMC's lower granularity, small size, and flexibility make it the optimal choice for future-proofing embedded systems and approaching advanced applications. By leveraging these features, developers can create more efficient, powerful, and adaptable systems ready to meet the challenges of the next generation.

Mark Littlefield, Systems Product Director, Elma Electronic

QMC, or VITA 93, is a new, small form factor I/O mezzanine standard from VITA. It is intended to perform much of the same functions as PMC or XMC, such as adding I/O expansion or other peripheral functions to a basecard, but in a much smaller form factor and with higher performance. 

QMC grew out of a need in the VNX+ standard (VITA 90). VNX+ required an I/O expansion capability, but XMC was too large, and other standard and non-standard I/O options all had shortcomings regarding performance, ruggedization, adequate standardization, or similar. QMC started as a study group in VITA (VITA 85.109), and when the study closed, the report showed a clear need for a new, small form factor I/O standard, thus VITA 93 was formed.

VITA 93 has several primary objectives:

• Mezzanine I/O expansion small enough to fit inside a 19mm VNX+ module
• Host side (PCIe) and I/O side defined connectivity
• At least PCIe Gen5 performance
• Air- and Conduction-cooled (and interchangeable between the two)
• Support for rugged environments (shock and vibration)

The working group wanted to ensure that QMC would be a suitable standard for a wide range of form factors and deployment platforms beyond VNX+, including VPX (and the up-and-coming VITA 100), CompactPCI and CompactPCIe, and PCIe edge finger carrier cards.

QMC was crafted from the beginning to support various cooling strategies. For simple lab-grade deployment a QMC with no heatsink or with a small finned heatsink is suitable. For more rugged deployments a metal conduction-cooled heatsink might be used. The carrier, however, is free to use whatever cooling structures the designer wishes to implement, so long as the mechanical envelopes of QMC are followed.

While QMC was defined specifically with backplane I/O in mind, there are many cases when front-panel I/O is desired. To address this, there are two documents currently in development to define companion modules for front-panel I/O; VITA 93.1 (XIOm) and VITA 93.2 (SIOm). XIOm is a small connector paddle-card with a single QMC-style connector that routes signals from the QMC I/O connector to industry-style connectors intended to be exposed to the carrier card front panel. 

SIOm is another small I/O module that matches the QMC Host connector to provide an extra-small front-panel I/O mezzanine capability. Carriers can be designed to support either a QMC or an SIOm, giving it and system designers flexibility in their I/O choices.

Already there is significant industry interest in QMC and its companion modules. Its compact size, high performance, and compatibility with both air and conduction-cooled platforms will enable vendors and integrators to find interesting applications to apply it.