Editing Expansion card (section)

===External expansion buses===
Laptops are generally unable to accept most expansion cards intended for desktop computers. Consequently, several compact expansion standards were developed. 

The original [[PC Card]] expansion card standard is essentially a compact version of the ISA bus. The [[CardBus]] expansion card standard is an evolution of the PC card standard to make it into a compact version of the PCI bus. The original [[ExpressCard]] standard acts like it is either a USB 2.0 peripheral or a PCI Express 1.x x1 device. ExpressCard 2.0 adds SuperSpeed USB as another type of interface the card can use. Unfortunately, CardBus and ExpressCard are vulnerable to [[DMA attack]] unless the laptop has an IOMMU that is configured to thwart these attacks.

One notable exception to the above is the inclusion of a single internal slot for a special reduced size version of the desktop standard. The most well known examples are [[Mini-PCI]] or [[Mini PCIe]]. Such slots were usually intended for a specific purpose such as offering "built-in" wireless networking or upgrading the system at production with a discrete GPU.