I was working with a PXI-8840 dual-core, so slightly different than OP's, but we were successful phenq where to buy in replacing the RAM using off the shelf parts just this past week.
The original 4GB stick it came with was this:
We just bought the exact same model*, with instead 8gb:
There wasn't any issues installing it, or being recognized.
8GB RAM DDR3 passend für National Instruments PXI-8840 QC SO DIMM 1600MHz ... 1PC NI PXI PXIE Empty Blank 3U CPCI Baffle.
PXIe-8840QC 8GB memory
in Hardware
Posted · Edited by SeanDelossantos
8GB RAM DDR3 passend für National Instruments PXI-8840 QC SO DIMM 1600MHz ... 1PC NI PXI PXIE Empty Blank 3U CPCI Baffle.