PXIe-8840 PXI Controller RAM for Controllers—PXIe-8840 Memory includes RAM chips to help you upgrade the memory read and write rate of the PXIe-8840, PXI-8840, and PXIe-8821 PXI Controllers. You also can replace the existing RAM. PXIe-8840 Memory is available in either 4 GB or 8 GB options.