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PXI expands to multiple processors
Martin Rowe, Senior Technical Editor- November 18, 2009
The PXI Systems Alliance has announced the PXImc (PXI MultiComputing) specification in two parts: hardware and software. Systems that comply with the new specification may have more than one processor module, thus increasing computing power.
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Think of PXImc like a local network for PXI/PXIe (PXI Express). A system's primary controller, called a Primary System Host, can communicate with a PXImc processor device over a PCI backplane, a PCIe (PCI Express) backplane, or a cabled PCIe port through an NTB (nontransparent bridge). With an NTB, the host controller can't see instrument cards across the bridge. The host can see only the PXImc device and instruments connected directly to the host, not through a bridge. Each PXImc device and the instruments behind it appear as a single PXI node to the Primary System Host. A PXImc device contains a processor, memory, a PCI/PCIe root complex, and an NTB.
The primary System host can be a stand-alone PC or a PXI/PXIe embedded controller. The connection runs from a stand-alone PC to a PXI/PXIe chassis through a cabled PXIe port. If you use an embedded PXI/PXIe controller as the Primary System Host, then the connection to a PXImc controller can be over the chassis backplane.
The figure shows two possible configurations. A PC connects to a PXI chassis where the chassis controller is a PXImc controller. In this configuration, the host can't see any of the chassis instruments. In the embedded-controller chassis, the host can see some instruments and the PXImc controller, but the host can't see the instruments beyond the PXImc controller.
The PXImc lets you expand your system beyond a single chassis. If you need a system with a PC as a primary host and need more than one instrument chassis or other PXImc-compliant device, you can connect the host to an external cabled PCIe switch to add ports.
You can download the PXImc hardware and software specifications at www.pxisa.org/Specifications.html.
