Advancing Embedded Systems with VITA 93: A New Era in Modular I/O for Aerospace and Defense

March 1, 2025

Aerospace and defense system designers are demanding scalable and high-performance I/O solutions. While traditional mezzanine standards have proven reliable, they often fall short of meeting modern bandwidth, size, and flexibility requirements. This challenge is particularly evident in aerospace and defense applications where high-speed data processing must align with stringent size, weight, and power (SWaP) constraints.

Current mezzanine solutions also face significant limitations in scalability, thermal management, and I/O density. These constraints can lead to compromised system performance and limited upgrade paths in applications where adaptability is crucial. This article explores how the new VITA 93 (QMC) standard addresses these challenges through its innovative QMC architecture, enabling unprecedented flexibility, scalability, and rugged reliability while maintaining compatibility with existing and future systems. It also covers how VITA 93 (QMC) builds on lessons learned from previous standards, blending their best features with new capabilities for the future.

VITA 93 (QMC) enables solutions for reduced-SWaP applications. A base single QMC measures just 26 mm by 78.25 mm, providing an optimal balance between component density and space efficiency. Compared to XMC modules it is substantially smaller, making it ideal for I/O interfaces in reduced-SWaP applications. (Image: TEWS Technologies)

In this article, system architects and design engineers will learn how evolving embedded system requirements are driving the need for flexible mezzanine solutions. Additionally, the challenges of traditional mezzanine standards and their impact on system design are outlined. Practical advantages of VITA 93’s modular architecture, including scalability from single- to quad-size implementations are also provided. The article also explains where QMC fits into the VITA ecosystem, benefits for single-board computer (SBC) and carrier designers, and how to leverage VITA 93 for future embedded system designs. Finally, readers will learn about the technical innovations of QMC, including advanced cooling options and high-speed interfaces.

Traditional Limitations

TQMC400 – Single size QMC: The first QMC module being released by TEWS Technologies. (Image: TEWS Technologies)

VITA 93 (QMC) builds on existing technology while addressing inherent challenges in current mezzanine card standards such as PMC and XMC. These issues include size, compatibility, thermal management, and limited expansion capabilities.

Modern systems demand compact solutions without compromising capabilities. Existing mezzanine cards, like XMC, were not designed to meet these stringent SWaP requirements, posing significant obstacles in aerospace, defense, industrial, medical and transportation sectors.

Depiction of an air-cooled QMC on a carrier card. (Image: TEWS Technologies)

As Dean Holman, President and Executive Director of VITA, notes, “The circuit boards used in older PMC and XMC designs are simply too large for today’s compact systems.”

With current mezzanine-card standards, system integration can sometimes become difficult: Air-cooled and conduction-cooled XMC cards are based on different designs and provide multiple I/O options. These factors mean that designers must spend extra time and effort ensuring everything will work together and sometimes have fewer options than they’d like.

Getting the heat off the cards can also be problematic. As field programmable gate arrays (FPGAs) and application specific integrated circuits (ASICs) become more powerful, they generate substantial heat, which current mezzanine cards often struggle to dissipate efficiently.

Additionally, the increased complexity and requirements of today’s systems leads to the need for system-health monitoring. Current mezzanine standards like XMC come only with a half-hearted approach to Intelligent Platform Management Interfaces (IPMI) and therefore require a higher integration effort.

Lastly, current mezzanine cards lack flexibility for growth as they come in fixed sizes – often too big – that cannot be easily changed, a situation akin to having a drawer that cannot be made bigger or smaller based on what you need to store. Engineers often end up either buying more capability than they need or not having enough space for all their requirements.

These challenges call for a new approach – one that is more flexible, can scale with changing needs, and works efficiently across different platforms. This is where VITA 93 (QMC) steps in.

Advancing Mezzanine Design

Depiction of a conduction-cooled QMC on a conduction-cooled carrier card. (Image: TEWS Technologies)

The VITA 93 (QMC) standard revolutionizes mezzanine-card technology, introducing a highly modular, flexible and scalable approach to I/O integration. Born from the VITA 90 working group’s development of VNX+, this standard addresses the growing need for adaptable, high-density I/O solutions in modern embedded systems.

VITA 90 working group engineers realized they needed a new way to add I/O capabilities to their systems; they wanted something that was not just smaller, but also more flexible than existing solutions. While VITA 93 (QMC) was initially designed to work with VNX+, it was always the aim to develop a new standard that solves existing limitations and can be used in broad range of PCIe-based systems like VPX.

“With VITA 90, also known as VNX+, it became apparent we really needed small mezzanine cards – much smaller than the mezzanine cards nowadays used on VPX,” VITA’s Holman explains. “The primary driver was being able to get something small enough to fit one or two of them on these really small-form-factor VNX+ boards.”

This focus on size efficiency, combined with the need for more versatile I/O options, led to the development of the QMC specification – a design that is proving valuable across multiple industries and applications.

Smaller by Design

A base single QMC measures just 26 mm x 78.25 mm, providing an optimal balance between component density and space efficiency. Compared to XMC modules, it is substantially smaller, making it ideal for I/O interfaces in reduced-SWaP applications.

“For certain applications where the primary use of this might be an I/O interface, I think you can’t get much smaller than a single QMC,” Holman says. “ I would say this is pretty close to what we can expect at least for the next 10 years.”

VITA 93 (QMC) supports up to PCIe Gen 6, which offers significant bandwidth capabilities while maintaining backward compatibility in the small form factor. It supports as many as x16 PCIe lanes in quad QMC configurations. The standard leverages the AccelerateHD Connector system by Samtec, ensuring reliable performance for high-speed applications.

The total thermal design power per single QMC is almost 30 W. For a double, triple, or quad QMC, just multiply the thermal design power for a single QMC by two, three, or four.

Single size conduction-cooled QMC with mounted heatsink. (Image: TEWS Technologies)

Scalability

The QMC architecture offers unseen scalability as it defines four card sizes within the standard, enabling the design of QMC cards that can cover a whole range of applications, starting from simple I/O functionality on single QMCs up to the highest-complexity solutions with the need for high bandwidth and high I/O count. Designs start with PCIe x4 and 40 I/ Os on a single QMC and can go up to PCIe x16 and 160 I/Os on quad QMC.

The standard scaling options include:

Single QMC: PCIe x4 with 40 I/Os
Double QMC: PCIe x8 with 80 I/Os
Triple QMC: PCIe x12 with 120 I/Os
Quad QMC: PCIe x16 with 160 I/Os

The 40 I/Os of a single QMC are organized into five I/O pipes each offering eight single-ended or four differential I/Os. Each I/O pipe comes with its individual ground supporting the integration of isolated interfaces.

Thermal Management

One of the key takeaways with VITA 93 (QMC) is that unlike previous standards like XMC or even PMC, the same card design can be used for either conduction- or air-cooled applications. In the past, that’s always been somewhat difficult and users often ended up needing two different products, as these two cooling approaches didn’t work together mechanically. That is not the case with VITA 93 (QMC).

Air-cooled and conduction-cooled QMCs are based on the same design. By adding a skyline heatsink to an air-cooled QMC it is converted to a conduction-cooled QMC. In addition, the conduction-cooling approach of VITA 93 (QMC) provides much better heat transfer from the QMC to the carrier than the XMC’s conduction-cooling approach.

VITA 93 (QMC) ensures interoperability between vendors through a well-thought-out mechanical concept. All mechanical components required for the mounting of the QMC card have to be provided by the carrier manufacturer, which makes it possible to fit any QMC on any carrier, whether it’s conduction-cooled or air-cooled, and independent of the QMC and carrier manufacturer.

With VITA 93 (QMC), system designers can optimize component placement and thermal management based on specific application requirements, as the standard defines variable stacking heights (9 mm, 11 mm, 14 mm, and 16 mm). The stacking height is solely defined by the carrier card, ensuring that all QMC cards will fit on the carrier card independent of the chosen stacking height and allows designers to most effectively use the PCB area underneath the QMCs.

Integration with VITA Ecosystem

VITA 93 (QMC) aligns seamlessly with other VITA standards like VPX and VNX+, offering a flexible, modular, and scalable I/O concept that enhances the entire ecosystem’s flexibility.

“I think it fits in perfectly,” Holman notes. “We specifically are structuring it so it supports VPX and other carrier-card standards, so everything that is being done now with 3U/6U OpenVPX can benefit from this.”

Moreover, VITA 93 (QMC) fits into the ecosystems of other standards, including those developed by PCISIG [Peripheral Component Interconnect Special Interest Group] and PICMG [PCI Industrial Computer Manufacturers Group] – for example, PCIe and CompactPCI-Serial – broadening its applicability.

Benefits for Single-Board Computer and Carrier Designers

The VITA 93 (QMC) standard introduces several transformative advantages, marking a significant departure from traditional mezzanine-card constraints.

Perhaps the most significant advancement is the ability to plug any QMC card into any QMC carrier without concerns about I/O routing, cooling method, or stacking-height compatibility. This universal approach eliminates the complex matching requirements for system designers with current mezzanine-card standards, which dictate specific cards that must be carefully paired with their carriers.

SBC designers can now focus more intensively on their core competencies, as VITA 93 (QMC) enables simplified I/O mapping by eliminating the need for complex routing schemes. Other advantages include support for multiple I/O functions on the same carrier and reduced design constraints that enable more specialized implementations.

Especially in SWaP applications where space is very limited, the variable stacking height concept with four defined heights (9 mm, 11 mm, 14 mm, and 16 mm, defined by the connector used on the carrier card) enables designers to integrate maximum functionality in limited space. For example, for VPX 1-inch or 1.2-inch carriers, an increased stacking height maximizes the component envelope available on the carrier.

The VITA 93 (QMC) standard supports multiple QMCs on a single carrier, offering advantages over XMC solutions that are typically limited to one or two functions per slot. This flexibility enables SBC designers to support diverse I/O requirements without compromising carrier design. Multiple functions can also be implemented without additional carrier complexity, while scalability is done easily by adding or changing QMC configurations.

In the VITA 93 (QMC) group there were more than 40 different companies participating in the standard’s development, many of them SBC vendors. “We expect more and more SBC vendors to offer QMC slots on their future SBC designs, benefiting from the advantages of this new standard,” says VITA’s Holman.

The highly modular, flexible, and scalable QMC architecture will bring the additional benefit of reduced development costs and minimal time-to-market for system designers, as highly diverse customer requirements can be met with integrated QMC cards.

VITA 93 (QMC) represents a groundbreaking advancement in mezzanine-card technology, offering unmatched modularity, flexibility, scalability, and reliability. With its well-thoughtout cooling concept, universal compatibility, and robust design, it sets a new standard for embedded systems across industries.

This article was written by Jan Zimmermann, General Manager at TEWS Technologies and Tim Tews, General Manager at TEWS Technologies (Pineberg, Germany) here .