(www.intel.com)—is revolutionizing data acquisition (DAQ). Tiger Yeh, PCI product manager for automation provider Advantech Corp. (www.advantech.com), based in Cincinnati, predicts PCI Express will be the trend of the future. “Maybe in five to 10 years, no one will be using the PCI bus.”
The new architecture’s features and scalability enable it to unify I/O across platforms such as desktop, mobile, server, communications, work stations and embedded devices, says Ajay V. Bhatt, director of Intel’s Digital Enterprise Group, Platform Architecture and Planning, in Hillsboro, Ore., in a white paper, “Creating a Third Generation I/O Interconnect.” Users implement a PCI Express link through multiple, point-to-point connections called lanes, he notes. Those multiple lanes can be used to create an I/O interconnect whose bandwidth is linearly scalable, he says.
“PCI Express is really forward looking,” says Brian Betts, National Instrument’s (www.ni.com) data acquisition group manager located at corporate headquarters in Austin, Texas. He says NI and its customers realize that the new architecture is poised to replace the existing PCI bus. One sign is that most new desktop personal computers (PCs) have at least one PCI Express slot, Betts points out. “We work quite a bit with the major [PC] vendors such as Dell (www.dell.com) and they’re telling us that moving forward, there will be a transition in which you’ll see both PCI and PCI Express in the same machine.”
More bandwidth
Going forward means taking advantage of the new architecture’s significantly higher bandwidth than PCI, Betts says.
That functionality is important because if an end user has several PCI devices on the same PCI bus, total available bandwidth is only 132 megabits per second (Mbps), notes Advantech’s Yeh.
But the new Intel technology will go to the 10-gigabits per second (Gbps) data-transmission limit of copper-wire technology through three increments, Betts explains. PCI Express 1 allows data passage at 2.5 Gbps, which is the signal frequency desktops and devices use now, he says. PCI Express 2 will transmit at 5 Gbps, and PCI Express 3 will allow the full 10 Gbps, Betts notes. “[But] what’s going to dictate when these occur will be the commercial availability of faster chip sets from vendors such as Intel.”
With its high bandwidth, the new architecture’s acquisition card can now provide high resolution and higher sampling rate, Yeh says. The card does this though shared switch topology, according to Betts. “Each PCI Express slot has its own bandwidth dedicated to memory.” But traditional PCI uses a shared bus topology, he says. “A standard desktop PC will have only a single bus with multiple slots, so each slot has to share bandwidth with other devices.” Both Betts and Yeh note that a single device can consume all that 132 Mbps bandwidth, if PCI is used.
So who will use PCI Express? One set of users includes those who simply couldn’t get the performance they desired out of a PC-based system with the PCI bus, Betts believes. The other group includes those who are building a new DAQ system who want to “future-proof” products against changing technology, he suggests.
In moving forward through such transition and replacement, however, “there will absolutely be support for the PCI bus,” he says. Introduced in 1991, it is still the standard on desktop machines, Betts says. He also notes that 90 percent of existing plug-in devices are PCI-based, with the remainder primarily using the industry standard architecture, or ISA, bus.
But PCI Express is the next standard for plug-in buses, Betts asserts. “It allows end-users to preserve their investment in software, which often is greater than their hardware investment.”
C. Kenna Amos, [email protected], is an Automation World Contributing Editor.
