In the world of embedded computing, as elsewhere, there is an ever-increasing demand to do more with less. As far as Computer-on-Modules are concerned, this specifically means packing more functionality and performance on a smaller footprint. This is why the PICMG (PCI Industrial Computer Manufacturers Group) is hard at work specifying COM-HPC Mini, a new, third-generation of credit-card-sized COMs for applications where space is limited yet required performance, interfaces and other needs are higher than second-generation COM Express Mini modules can address.
Technology doesn’t stand still, so it’s little surprise that hot on the heels of the launch of the new high-performance COM-HPC standard for client and server modules, the PICMG is already working on a high-end mini form factor. It is designed for small yet extremely performance-hungry applications that are not supported by COM Express Mini. The forthcoming COM-HPC Mini standard is the next step in the evolution of credit-card-sized Computer-on-Modules. This started with the DIMM-PC module specification back in the 1990s.
A look at the blueprints for COM-HPC Mini
The PICMG announced detailed plans for a small form factor expansion of the high-end COM-HPC standard in early 2022. The new COM-HPC Mini modules will have a considerably smaller footprint than the bigger client and server size modules. Measuring just 95×60 mm, COM-HPC Mini modules are half the size of the smallest COM-HPC Client module Size A. Such extremely small modules are required to embed computer logic in building and industrial automation control systems or portable test and measurement devices, to give just a few examples.
Specification:
Beyond shrinking the footprint, the COM-HPC Mini specification comes with a high-performance pinout. It provides 400 signal pins, as compared to COM Express Mini’s 220 pins. The new standard is determined to satisfy the rising interface needs for edge processing. Extensions include up to 4x USB 4.0 with full functionality including Thunderbolt and DisplayPort alternate mode, PCIe Gen4/5 with up to 16 lanes, a second 10 Gbit/s Ethernet port and much more. Add to that the fact that the COM-HPC Mini connector is also qualified for bandwidths of more than 32 Gbit/s – enough to support PCIe Gen5 or even Gen6 – it is clear that it’s capabilities go well beyond those of COM Express Mini, which is limited to PCIe Gen3 with a clock rate of 5.0 GHz and 8 Gbit/s.
However, it is not just COM Express Mini users who can benefit from the small form factor expansion of COM-HPC. COM Express Compact and COM Express Basic designs also stand to gain by migrating to this new standard. Especially for the high-volume low- to mid-end segment of these COM Express form factors, COM-HPC Mini offers great space-saving potential without loss of performance and virtually no loss of interfaces. So by using COM-HPC Mini to migrate larger designs towards credit-card-sized modules, COM Express Compact and Basic users will be able to speed up the miniaturization of their existing system designs.
Market launch expectations
With the R&D departments of major computer module manufacturers such as congatec working flat out to finalize the specification within the PICMG, chances are that the first COM-HPC Mini modules will hit the market within a few months. Such a rapid market launch is made possible in part by the close relationship with semiconductor manufacturers such as Intel, who share their latest processor technology via early access programs. First prototypes of Intel Core processor based COM-HPC Mini modules and matching carrier boards are already in development today. So, developers looking to initiate innovative next-generation designs can start to evaluate COM-HPC Mini immediately.
No rush to change
Packing extremely high performance into a small computing module, COM-HPC Mini clearly targets the high-performance area of credit-card-sized COMs, such as mobile and portable systems in medical technology, rugged battery-powered tablets and handhelds, or size constrained automated guided vehicles (AGV) and autonomous mobile robots (AMR). COM-HPC Mini will in all likelihood quickly become the preferred choice for this segment. There are also countless compact designs that require neither highest available performance nor the latest interface technology with extreme bandwidth.
For developers of such systems, there is no pressing need to change standard when upgrading or developing new designs. COM-HPC Mini should be seen as a complementary standard to address evolving demands. It is not a replacement for COM Express Mini or, for that matter, other small form factor standards. Especially since the latter are focused on low power designs that don’t require highest performance and bandwidth. A look at the evolution of credit-card-sized modules shows that the market needs and supports parallel standards for decades.
DIMM PCs are where it all began
The era of credit-card-sized COMs started at the turn of the millennium with the DIMM-PC module specification. Measuring 68×40 mm and based on a100 MHz x86-compatible STPC from STMicroelectronics, DIMM PCs were about the size of a credit card. It came with an 144‑pin SO‑DIMM connector. Providing an at the time unprecedented selection of I/O interfaces on such a small footprint, this connector set the trend for later developments.
Even then, and much like the new COM-HPC Mini modules today, the main targets of DIMM PCs were applications that needed to be small, power efficient and mobile. While these features sound very similar to today’s modules, the performance of those first-generation credit-card-sized modules and the number of available interfaces were a long way from what the embedded world needs today. Significantly, there was not enough space to execute graphics on the 144-pin edge connector of the first DIMM PCs. An extra connector was needed to provide true industrial-grade computer module functionality.
The DIMM PC form factor’s limitations became obvious as newer, more powerful x86 processors and chipsets came to the market. Introduced in 2003, the Intel Pentium M simply did not fit on the DIMM-PC dimension. This essentially was only suitable for lower-power processors. This include the 568 ZFx86 from ZF Micro Devices, with a clock speed of 128MHz, or the STPC Elite from STMicroelectronics.
The era of COM Express Mini begins
Efforts to define a brand-new specification that would take the general computer module concept, and credit-card-sized modules with it, to the next performance level began in 2003 when the first plans for COM Express were presented. It was officially adopted by the PICMG standardization committee in 2005. The COM Express specification has been continuously developed and expanded until the current Rev. 3.0. As an industry first, COM Express specified a single standard to cover all common module sizes: COM Express Basic (125×95 mm), COM Express Compact (95×95 mm), and COM Express Mini (84×55 mm). This uniform ecosystem was a major cornerstone of the subsequent success of the COM concept. It encouraged automation suppliers worldwide to base their designs on the COM Express specification. It meant that they could use the same standard for their entire portfolio of solutions.
COM Express Mini modules started to properly take off when Intel launched the first Atom processors in 2008. Offering an all-in-one system controller, i.e. combining the north and south bridge, they did fit snugly on these credit card modules. Since then, COM Express Mini modules with AMD Ryzen or even 8th generation Intel Core processors have also become available. To this day, however, Intel Atom processors remain dominant in this size. The portfolio of congatec modules, for example, ranges from the third Intel Atom generation through the fourth and fifth to the current Intel Atom x6000E Series processors as well as Intel Celeron and Pentium N & J processors (codename Elkhart Lake).
Enter SMARC and µQseven
The following decade saw the launch of two further vendor-independent specifications: SMARC (82×50 mm) and µQseven (70×40 mm). Hosted by the SGET (Standardization Group for Embedded Technologies), these specifications were the industry’s answer to two shortcomings of COM Express Mini. The first goal was to broaden the processor range to allow integration of Arm processors. These were becoming increasingly popular but were not supported by COM Express Mini.
The second aim behind SMARC and µQseven was to cut costs by hosting just one edge card connector on the carrier board. As opposed to COM Express, where both, the module as well as the carrier required a connector. By comparison, SMARC and µQseven use a single MXM connector that was developed for high-speed graphics cards. Further, it is commonly deployed in notebooks. It offers 314 pins, which is 43% more pins than COM Express Mini and 37% more than µQseven. SMARC dominates the market for credit-card-sized modules today.
Co-existence will prevail
With the upcoming COM-HPC Mini, system developers who have based their designs on one of those existing credit-card standards may well be wondering whether they must soon switch to the new form factor. But unless they are designing next-generation systems for highly performant yet extremely small applications, there is no rush nor compulsory reason to change. If the history of computer modules is anything to go by, the market will continue to demand that vendors support existing designs for a long time. As a result, COM Express Mini, SMARC and µQseven will happily co-exist alongside COM-HPC Mini for years to come.
What the introduction of the new COM-HPC Mini standard will do, however, is turn COM-HPC into the most complete computer module definition yet offering the broades scalability in regards to performance, footprints and supported silicon, as COM-HPC does support x86, Arm and accelerators like GPUs, FPGAs and ASICs. Collectively, this latest generation of Computer-on-Modules will provide the high-end in each of its form factors to cover the most demanding use cases for which there are no alternatives in other standards today.
About the author:
Zelkjo Loncaric is Product Marketing Managerat congatec.
