Dell included a 16X PCI-E slot with the Dell SC420. Oddly only enough pins for an 8X card are present, and they placed 2 dividers preventing the use of a 16X card even though it’s a 16X slot. Knocking out those two dividers and running a 16x card at 8x is the plan. With the minimal effects of 8X vs. 16X, this modification was a go! [via] Link.
Dell SC420 PCI-Express Modification