The PXI-5122EX did have the same specifications as the PXI-5122, as it used the same analog front end circuitry. The main difference was that it allowed for the limited addition of custom logic in the firmware by the end user. The PXI-5122EX has been EOL'ed, and is no longer supported or sold.
The new NI Reconfigurable Oscilloscope, the PXIe-5171R, features an open and user-programmable FPGA with LabVIEW FPGA, and allows for the complete customization of the device. For more information on this exciting product, see its product page:
http://sine.ni.com/nips/cds/view/p/lang/en/nid/212657
http://www.ni.com/datasheet/pdf/en/ds-548
I hope this helps!
Regards,
Nathan
Systems Engineer
SISU