[copied from superuser.com]
I'm duplicating an existing compact PC; I'd love to replace it with modern components, but for various reasons I can't.
I'm having a tough time finding the correct 32-bit PCI right-angle riser card. I bought a new one, and the dimensions are the same, but the wiring is different, and the system doesn't recognize the inserted card (an audio card).
The old, working riser (green in the pictures below) has five capacitors, and the wiring doesn't look straight-through. When I toned it out, it seemed to be straight-through, although several pairs of adjacent pins were connected. It's at least a three-layer board with an internal ground plane.
The new, not-working-for-me riser (red) is pretty clearly straight-through, with no components other than the connector. I toned it, and no adjacent pins are shorted. It's just two layers; no ground plane.
Strange thing: plugging the audio card straight into the motherboard works fine, which suggests that a straight-through riser should work.
So, the question is: are there different types of PCI riser cards? How can I find one that's electrically equivalent to the old one? (And, why won't the new straight-through riser work, when the audio card works if plugged directly into the motherboard?)