Originally Posted by Mongrel
The PCIE standard has unfortunately not maintained full backward or forward compatibility over it's revisions every 3 to 4 years. This has lead to sometimes needing a motherboard change to upgrade PCIE peripherals and with mobo changes often the processor also needs to be changed. The opposite compatibility problem sometimes happens when a new mobo does not work well with older standard PCIE add-on boards. Sometimes there is just a loss of performance caused by the imperfect compatibility. I've hit this situation often enough that I don't bother trying to upgrade PCs very often anymore because it's usually more cost effective to buy new (when I count my time as money).