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Cabled PCI Express as a Standard
Interface for Virtual and Synthetic
Instruments
Overview
Cabled PCI Express is a cabled serial bus used for high-performance interconnect of system components. It is based on
PCI Express and so provides a scalable, high-bandwidth, low-latency bus. In measurement and automation, cabled PCI
Express is very appealing to high-performance applications using a host PC for measurement processing and analysis.
For example, cabled PCI Express is currently used to connect
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Figure 1. NI MXI Express uses cabled PCI Express to connect a PC to PXI The x1 MXI Express form factor shown above uses a PCI Express slot in a desktop PC to connect to a PXI chassis. The ExpressCard form factor shown below supports a x1 cabled PCI Express link to a PXI chassis using the same cables. Thus the PXI module and cables are common to both laptops and desktops allowing for higher reuse. Document Version 1 2 © 2006 National Instruments Corporation. All rights reserved.
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Cabled PCI Express as a Standard Interface for Virtual and Synthetic Instruments Figure 2. NI MXI Express uses cabled PCI Express to connect a Laptop with ExpressCard to PXI When MXI-1 first launched in 1991 it provided 10MB/s bandwidth. This was state-of-the-art and used commercial technologies available at that time (see Figure 3). By incorporating cabled PCI Express into the MXI product line can now sustain nearly 800 MB/s. Document Version 1 3 © 2006 National Instruments Corporation. All rig
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Figure 3. Cabled PCI Express makes MXI Express 80X higher bandwidth than MXI-1 While bandwidth has dramatically increased, the costs of these links have decreased. Figure 4 shows how the price per bandwidth has dropped significantly over the last 15 years. Figure 4: From $450/MB/s to $2.25/MB/s – Cabled PCI Express Helps Decrease Price per Bandwidth MXI Express x1 for PXI chassis cut the cost per MB/s in half from $19/MB/s to $9/MB/s. MXI Express x4 for PXI Express chassis cut that further to $2
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Cabled PCI Express as a Standard Interface for Virtual and Synthetic Instruments The focus of the SIWG has been primarily on the SI concepts as applied to RF stimulus and measurement systems. Data intensive applications, like RF testing, require a high-bandwidth, low-latency bus to connect the IF digitizers to the processor (see Figure 5). Figure 5. Synthetic Instrument RF Block Diagram For example, to digitize a 50 MHz wide RF signal requires 100 Mbytes/s of bandwidth (at 2 bytes of resolution
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Whitepapers NI offers a Designing Next Generation Test Systems Developers Guide. This guide is collection of whitepapers designed to help you develop test systems that lower your cost, increase your test throughput, and can scale with future requirements. To read the entire developers guide, you can: Download the PDF (90+ page) version or view the web-version of the Designing Next Generation Test Systems Developers Guide. Document Version 1 6 © 2006 National Instruments Corporation. All rights r
