Here's some interesting results of a small experiment I did... One day I remembered that different PCIe speeds are supposed to be "electrically compatible" with each other. That is, a PCIe 16x card should work in a 1x slot, but putting the card in it is not possible because of the physical difference of the connector.With some googling around I found some PCIe 1x to 16x slot adapters but with ridiculously high prices. I didn't really need one so I wanted something less expensive. From ebay I found some stores selling PCIe 1x to PCIe 1x riser adapters for a very cheap price (just a few euros). For fun I ordered one:This one has a ribbon cable, which seems maybe a bit fragile but not much to complain for the price I got it (About 6 euros).Here's the problem with the connectors: The 1x slot is too short for the 16x connector on the card.And here's a simple solution. Just cut off the end of the 1x slot to allow the 16x width connector to go in; The 1x pins will connect properly... I used a small blade which I heated with a lighter.Not too pretty......But it worksHere is the GeForce 8400GS card with the ribbon cable attached. That isn't obviously going to go into the case normally.This is good enough for testing. A more permanent solution could use a "low profile" bracket for the card (I believe the 8400GS came with one but I have lost it) or the card could just be mounted on whereever there is a screw hole to attach it to.Power on, and......install drivers...It works just like a normal card, just 1x bus speed.The d3dbandwidth numbers aren't too great, but pretty much at the level I expected:I proceeded with some quick SoftTH tests, and I was surprised that the performance is not at all bad; As long as the secondary screen resolution is not set too high (1024x768 is good, 1280x1024 is pushing it a bit), performance is better than I expected. I didn't (yet) do any detailed performance comparisons but here's some quick numbers*:Flight Simulator X, 4800x1200 resolution, 1600x1200 on side monitors: 40 FPS with 16x card, 32 FPS with 1x.rFactor, 3840x1024 resolution, 1280x1024 on side monitors: 110 FPS with 16x card, 71 FPS with 1x.rFactor, 3840x1024 resolution, 1024x768 on side monitors: 121 FPS with 16x card, 119 FPS with 1x.Armed Assault, 4800x1200 resolution, 1280x1024 on side monitors: 64 FPS with 16x card, 55 FPS with 1x.Armed Assault, 4800x1200 resolution, 1024x768 on side monitors: 64 FPS with 16x card, 64 FPS with 1x.These results would suggest that at 1024x768 side resolution the 1x bus has enough bandwidth to not cause much of a bottleneck even at high framerates, but 1280x1024 is beginning to "cap" the FPS. Even at 1600x1200 side resolution the FPS still can be pretty good.Some notes:- Seems like a pretty easy and very cheap way to add a second PCIe card into a motherboard with only one 16x slot- I suspect the ribbon cable may cause trouble with some cards, it adds quite a bit of extra length to the connector (but a non-ribboned one could be used as well)- Are all PCIe 16x cards also compatible with 1x speeds?- Propably could also be done for a 4x slot in much the same way- You could forget about the riser altogether and just "mod" the motherboard connector directly, assuming there are no other components in the way- Sawing the extra bits off the card would work too, but would propably require some careful cutting to not cut any other internal traces- a PCIe 2.0 compatible card (when used with PCIe 2.0 motherboard) should double the bandwidth when used this way as well* These are done by using the GF8500GT for the 16x slot and the GF8400GS for the 1x slot result. The 8500GT is generally faster but I suspect it should not make much difference in this case.