PCI and PCIe use the same basic process to "discover" PXI(e) modules based on both standards. PCI(e) modules are identified by a bus number and a device number In PCI, there can be up to 16 devices on the bus (actually PXI 8 devices, including bridges at each end), indicating the bus number of the bus segment and the device of each module on that bus segment. In PCIe, the situation is slightly different because it is a point-to-point system (rather than a multipoint system like PCI), where each module has its own bus number. In both cases, PCI is limited to 256 buses, which must include the controller's internal buses and any bridges or virtual buses associated with them. Thus, for PCIe, the theoretical maximum number of modules that can be connected is equivalent to PCI, but still quite large compared to the number of buses in a typical single chassis.

Some PCs also seem to have BIOS issues related to enumerating long chain bus connections, so PXIe chassis vendors may strongly recommend the use of tested embedded or remote controllers and provide a list of these models. It is not safe to assume that because a controller model is from a specific manufacturer that all controllers from that manufacturer will work properly, which is certainly not the case. The problem appears to be due to the fact that PCs typically do not expect a large number of PCIe buses and there is a conflict between supporting large bus counts and the user's need for fast boot times.

    The X-Series Data Acquisition (DAQ) devices contain 32 analog input channels (AI), 4 analog output channels (AO), 48-bit digital I/O lines, and 4 counters, and the X-Series Data Acquisition (DAQ) devices have a sampling range of 250 kS/s for multichannel switching AIs up to 2 MS/s for synchronous sampling AIs. The Synchronous X-Series data acquisition devices integrate up to 16 A/D converters in a single device at rates up to 2 MS/s per channel, so engineers can sample all analog input channels at high sample rates while avoiding phase shifts. But also because of this, synchronized X series devices will need to send a large amount of data back to the host PC, data throughput will reach 64MB / s, plus the accompanying AO channel, digital I / O and counter operations, a single device will reach a total data throughput of 100MB / s, which is actually the maximum value of the PCI bus. Thus, the X-Series capture cards choose to use the high data throughput PCI Express bus.            

      PCI Express offers many advantages in data acquisition applications, including dedicated bandwidth of up to 250 MB/s in each direction for each device. Users can take advantage of the extra bandwidth to capture larger amounts of analog, digital, and counter data; and by utilizing the dedicated bus, engineers can more easily expand their systems to include multiple data acquisition devices. The new X-Series devices integrate the original PCI Express interface to provide 250 MB/s PCI Express bandwidth instead of the PCI to PCI Express bridge interface. This limits the device bandwidth to the PCI bus bandwidth. The devices are also optimized for low-latency I/O, which improves performance in control and single-point applications.