Bridge Chip Imparts A Universal Spin To CompactPCI Single-Board Computer

Until now, CompactPCI boards have lacked a certain degree of flexibility. For instance, system host boards were designed to work in the system slot of a CompactPCI backplane, while peripheral boards filled peripheral slots. But the PowerCore CPCI-680 from Force Computers breaks that mold. It's a "universal" board. Breakthrough PCI-to-PCI bridge technology makes it feel at home in any type of slot in the CompactPCI backplane. The board automatically switches between system or peripheral operating modes without any software or hardware changes.

Typical CompactPCI boards employ either a transparent or embedded PCI-to-PCI bridge, depending on the slot type. The CPCI-680, on the other hand, uses Force's new Sentinel chip. This chip incorporates all of the functionality of a transparent and embedded bridge, with no additional software or specialized drivers needed.

The chip also has a host of other features. It facilitates multi-computing, for instance. From a hardware point of view, all of the registers needed to support multicomputing are built into the chip. On the software side, Force is a member of the Multicomputing Standard PICMG 2.14 committee, which is standardizing the mechanism to communicate via the CompactPCI backplane. Based on standard network software, this protocol is transparent for the application whether it runs via CompactPCI or Ethernet. "The idea is really to have a fast communication link via CompactPCI," says Christoph Adam, technical marketing manager for Force Computers. "It's important to be processor- and operating-system-independent."

Those multicomputing features also are evident in the chip's support of intelligent I/O (I₂O). Large FIFO memories are built into the chip for even faster communications via the backplane.

Another benefit of Sentinel is availability support. This term refers to the chip's support of hot swap not only for intelligent I/O boards, which already exists with embedded PCI-to-PCI bridges, but also for the non-intelligent ones. These boards typically use a transparent bridge that lacks the hot-swap registers for CompactPCI. Because Sentinel has these registers built in, it can be used to design a hot-swappable, non-intelligent I/O board. This is an indication of one possible use for the Sentinel chip in the future, since Force has no plans to market the chip by itself.

The company paid specific attention to increasing the chip's I/O bandwidth. To achieve high data throughput, Force has placed deep buffers on the chip to collect a lot of data and then send it over the CompactPCI backplane.

Another significant aspect of the chip is its support of message-signaled interrupts (MSIs) as defined in PCI specification 2.2. To avoid bottlenecks in real-time mission-critical systems, the Sentinel chip doesn't have to use the four interrupt lines on the CompactPCI backplane to indicate a service request to the processor. Instead, through the MSI feature, a chip in a peripheral slot utilizes a PCI memory write access over the CompactPCI bus. It writes to the Sentinel on the system-controller board. This board initiates a local interrupt, assuring predictable response times even for 16-slot systems.

Adam also pointed out a factor that Force refers to as longevity. To the company, this means true embedded life-cycle support. It does its designs in-house and has its own ASIC team. He states that in essence, Sentinel is backed by Force's proven track record and commitment to the embedded market.

"The idea is to have a silicon roadmap, not just standalone silicon," notes Adam. Force wants to react quickly to new trends, technologies, and interfaces and integrate these into the next revision of the chip. An architectural overview of the chip is shown in Figure 1.

Getting back to the board itself, the PowerCore CPCI-680 is the first product from Force Computers to use the Sentinel technology. "Customers who want to have a very powerful real-time system normally have to purchase a system-slot controller and I/O peripheral boards," says Gerhard Mayr, product marketing manager. "Often, these are not compatible with each other, and software engineers have problems developing the code to handle two different products. One of the key features of the CPCI-680 is that customers can leverage off the Sentinel bridge by just using a single product. One board runs in the system slot and an identical board runs in the peripheral slot."

The CPCI-680 is a PowerPC-based single-board computer. It's not based on just any PowerPC, but Motorola's supercomputer-on-a-chip—the G4 running at 400 MHz. It has a 128-bit-wide level-2 cache (up to 2 Mbytes) running at half the processor speed.

Mayr points to the power consumption of the G4. The PowerPC already had very high performance while consuming very low power. Now the G4, considered a supercomputer because it processes one-billion floating-point operations per second, consumes only 5 W. This helps to alleviate cooling problems and also reduces power-supply demands. "It's really an advantage," states Mayr.

The G4 also contains AltiVec technology, an on-chip 128-bit vector-processing unit. "In the embedded world, this AltiVec technology can easily be used for ongoing floating-point operations, such as media processing and vector graphics. A speech-compression algorithm is a good example," states Mayr. "We have gotten feedback from customers telling us that they can save on their DSP development by using the AltiVec technology."

To boost performance, the company is using the latest synchronous DRAM technology. It will be 100 MHz at first, but scalable up to 133 MHz in the next four to five months. The board is able to handle up to 1 Gbyte in a single slot. "Who needs a gig for real-time applications?" asks Mayr, rhetorically. "Telecom and datacom come to mind. Take unified messaging systems, for example, where you have a huge database that needs to run very fast. You want to eliminate accesses to the hard drive. Here, the gigabyte of memory is absolutely essential."

The CPCI-680 has up to 256 Mbytes of memory on board. A memory module can go on top of that, should the user need more. For previous-generation boards, Force invented the stackable memory module. Customers can maintain their investment in memory by just placing another module on top of the one that's already installed.

The CPCI-680, a single-slot 6U card, includes two Fast Ethernet controllers (Fig. 2). According to Mayr, developers of telecom applications often want two independent Ethernet interfaces: one for diagnostics and the other for transferring data. The board also offers 16-Mbyte flash and an optional IDE flash-disk socket. Each board has two PCI mezzanine-card slots and two serial interfaces. Other variants offer an on-board, fast-wide SCSI-2 and four additional serial interfaces for extended communication and mass-storage needs.

As for software support, the CPCI-680 supports such real-time operating systems as LynxOS, OSE Delta, pSOSystem, and VxWorks/Tornado. Also important is its support for Unix-type operating systems, such as Linux.

So what are the target applications for the CPCI-680? Aside from those already mentioned, Force is targeting IP telephony gateways, access concentrators and DSL access multiplexers, and ATM or IP Layer-3 data-communication switches. It's also aiming at Internet routers, virtual-private-network servers, voice-over-IP systems, and systems that do speech processing and recognition as well as image and video processing. Look for it to pop up in control and data-processing functions in base-station controllers and transceiver stations in wireless local loops, as well as any other real-time applications that require scalable multi-computing capability.

Force Computers Inc., 5799 Fontanoso Way, San Jose, CA; (408) 369-6000; fax (408) 371-3382; www.forcecomputers.com.