The need for a new specification to complement COM Express is easily explained: As a result of the digital transformation, the demand for embedded computers to provide high-speed performance is growing. To serve the new class of embedded edge servers, scalability must be limitless. With its 440 pins, COM Express does not have enough interfaces for powerful edge servers. The performance of the COM Express connector is also slowly approaching its limits: While COM Express can easily handle the 8.0 GHz clock speed and 8 Gbit/sec throughput of PCIe Gen 3, the verdict is still out regarding whether the connector meets certain technological advances such as PCIe Gen 4.
Three COM-HPC Module Types are defined: the Client Module Fixed Input Voltage; Client Wide Range Input Voltage, and the Server Module with a Fixed Input Voltage. They serve different user needs and different markets. The Client and Server Module definitions and pinouts have many things in common, but they are separate. Client Modules should not be used with a Carrier board designed for Server Module use, and Server Modules should not be used with a Carrier board designed for Client Module use.
COM-HPC Feature Summaries
The COM-HPC Client Module Type targets use in high end embedded client products that need one or more displays, a full set of low, medium, and very high bandwidth I/O, powerful CPUs, and modest size. Typical uses are in medical equipment, high end instrumentation, industrial equipment, casino gaming equipment, ruggedized field PCs, transportation and defense systems, and much more. Client Modules typically will use SO-DIMM or soldered–down memory. Up to four SO-DIMM memories may be supported on COM-HPC PCB Size C (160 mm x 120 mm).
Client Modules operate from either a fixed 12V power source, or optionally implement wide range of input power supplies, over a range of 8V to 20V. This facilitates their use in battery-powered equipment. Client Modules can accept up to 251W of input power (using the connector vendor recommended 20% current capacity derating) over the 28 Module VCC pins, at the 8V end of the power in range. This allows CPUs with about up to 100W dissipation or more to be used on Client Modules that implement a wide range of power input. Some situations may require a more conservative current derating. Higher power operation is possible if the fixed 12V supply operation is used.
The COM-HPC Server Type targets use in high-end headless (no display) embedded servers that require intensive CPU capability, large memory capacity, and lots of high bandwidth I/O including multiple 10Gbps or 25Gbps Ethernet, and up to 65 PICe lanes, at up to PCIe Gen 5 speeds. Typical uses are in embedded server equipment ruggedized for use in field environments and applications such as autonomous vehicles, cell tower base stations, geophysical field equipment, medical equipment, defense systems, and much more. Server Modules will typically use full-size DIMMs. COM-HPC Server Modules are typically larger than the Client Modules, but Server vendors are free to use any of the five defined COM-HPC module sizes. The sizes are summarized in Section 2.5 below, and a list of Server Module features may be found in Section 2.6 ‘Client and Server Interface Summary and Comparison’ in the full Specification. Up to eight full size DIMM memories may be implemented on the largest COM-HPC module form factor.
The Server Modules use fixed voltage 12V input power. Server Modules can accept up to 358W of input power (using the connector vendor recommended 20% current capacity derating) over the 28 Module VCC pins, at the low end of the 12V power in range. This allows CPUs with up to about 150W dissipation to be deployed on Server Modules. The limit is subject to considerations such as the connector pin derating used, the number of memory sockets used, and other power consumers on the Module.
Module Size Overview
Five COM-HPC Module PCB sizes are defined:
- 95mm x 120mm Size A (Recommended for Client use)
- 120mm x 120mm Size B (Recommended for Client use)
- 160mm x 120mm Size C (Recommended for Client use)
- 160mm x 160mm Size D (Recommended for Server use)
- 200mm x 160mm Size E (Recommended for Server use)
Note that the mounting holes adjacent to Module connectors J1 and J2 are offset from the connector long axis center-lines. This is done deliberately to provide a visual cue as to the proper mounting orientation of the Modules onto the Carrier boards.
COM-HPC uses a pair of 400 pin high-performance connectors, for a total of 800 pins. The connector system allows signaling rates up to 32 Gtps, suitable for PCIe Gen 5. The connector system allows for 10 mm or 5 mm Carrier – Module stack heights.
Non – x86 Implementations
COM-HPC Client and Server Modules are not restricted to traditional x86 CPU implementations. Modules that host PCIe targets such as FPGAs or GPUs are allowed. PCIe signal details on this matter are provided in the full Specification.
COM-HPC Modules may host traditional x86 systems or may host alternative ARM or RISC CPUs or may host PCIe targets such as module-based FPGAs or GPUs.
Module and Carrier Board Out-of-Band Management Control
COM-HPC Module and Carrier boards may support out-of-band (OOB) management features. These features may be implemented on COM-HPC Server or Client systems. Traditionally OOB management is more of a server-class feature, but the option is there for both COM-HPC Clients and Servers. A separate PICMG document will describe the COM-HPC OOB management features in detail.