All i can imagine atm is to buy 2 server-chassis and use the bottom one as “pcie expander”, the top one for mainboard and connect them with pcie ribbon cables.
Well, i hopefully don’t need a “external interface card” for that 30-50cm if you mean redrivers, but yeah he also has redrivers.
A chassis is what i need!
None exist, there’s no demand for such a thing. What you want is going to be custom made, and there’s two ways about it. First option, buy the super expensive external chassis, second, do some in-house metal working…
Cheapest way is modifying a big chassis to hold a second chassis inside it, like one of those double wide cube cases. Cut down a cheapo second chassis so it’s pretty much just the skeleton that holds cards, and weld / rivet it in opposite the main section. Shouldn’t need any complex tools, just basic angle grinder, pop rivet tool, some flat files for the sharp bits, drill, HSS bits, etc.
In industrial applications where you need a lot of PCI cards, an external chassis is used for just the cards. The processor board stays in its own box, shielded cable connect the two, hence the “external interface card.”
Here’s another chassis from One-Stop, you can see the insides a bit better. This would sit next to the chassis containing the processor, and a cable connects the two.