I honestly don't know what the best solution is. Have you compared the mechanical spacing with the ATX riser standard?
http://www.formfactors.org/developer%5Cspecs% … X_Spec_V1_0.pdf

Are you sure the riser board actually works with your motherboard? Most boards that use risers are made so they can only use specific riser board models; if your motherboard does not support risers with ISA slots it won't work.

As for the riser board you have, Guanghsing also makes riser boards for specific motherboard models that go into proprietary case formats. Maybe it's one of those?

The case you have may look like a 2U server case, but it isn't one. Most desktop cases that use risers can only be used with specific riser cards made for the case.

The riser fits in a PCI slot, it's not a proprietary slot for a specific case. Or so I thought. The product page makes no mentions of any specifications, it's literally "2xPCI, 1xISA Slots Riser Card for 2U Chassis". And when I look at pictures of 2U servers, and after weeding out all the non-standard cases with proprietary motherboards and risers (and that's a lot), the ones that I find that accept ATX look exactly the same as mine from the back. Same motherboard backplate dimensions, same apparent distances between the various elements. But obviously I must be wrong somewhere, as stuff simply doesn't fit.

Thanks for the link, I'll have a go at measuring my card.

jarreboum wrote:

And when I look at pictures of 2U servers, and after weeding out all the non-standard cases with proprietary motherboards and risers (and that's a lot), the ones that I find that accept ATX look exactly the same as mine from the back. Same motherboard backplate dimensions, same apparent distances between the various elements. But obviously I must be wrong somewhere, as stuff simply doesn't fit.

One thing that life has taught me is to avoid thinking "apparent distances" can be a guide for precisely fitting parts to actually fit 😊 . It makes the difference between, say, a 1/8" machine screw and a 3 mm machine screw, which may look similar, but certainly are not. The 1/8" machine screw will not hold in a 3 mm hole, while even though it's possible to fit a 3 mm machine screw in a 1/8" hole, the screw threads will get trashed and it might be impossible to remove the screw afterwards.

Find yourself the technical manual of the product you are comparing with and check the measurements listed against those of your own case (you may also have to look at a 2U server motherboard manual) - use calipers or a ruler when making measurements on your own case, not your eyeball!