Nope, not limited by the PCI bus, as it doesn't use that to transfer data, just supply power. It connects via SATA1, same speed as the ACARD now appears to (even in SATAII mode). So they are almost on par in performance. That's the disappointment, really, that 4 or 5 years of massive tech advances hasn't produced a faster RAM drive, simply becase it's being bottlenecked by poor interfacing.