daughtercard, mezzanine board or piggyback board is an expansion card that attaches to a system directly. Daughterboards often have plugs, sockets, pins or other attachments for other boards. Daughterboards often have only internal connections within a computer or other electronic devices, and usually access the motherboard directly rather than through a computer bus. Such boards are used to either improve various memory capacities of a computer, enable the computer to connect to certain kinds of networks that it previous could not connect to, or to allow for users to customize their computers for various purposes such as gaming. Daughterboards are sometimes used in computers in order to allow for expansion cards to fit parallel to the motherboard, usually to maintain a small form factor. This form are also called riser cards, or risers. Daughterboards are also sometimes used to expand the basic functionality of an electronic device, such as when a certain model has features added to it and is released as a new or separate model. Rather than redesigning the first model completely, a daughterboard may be added to a special connector on the main board. These usually fit on top of and parallel to the board, separated by spacers or standoffs, and are sometimes called mezzanine cards due to being stacked like the mezzanine of a theatre. Wavetable cards (sample-based synthesis cards) are often mounted on sound cards in this manner. Some mezzanine card interface standards include the 400 pin FPGA Mezzanine Card (FMC); the 172 pin High Speed Mezzanine Card (HSMC); the PCI Mezzanine Card (PMC); XMC mezzanines; the Advanced Mezzanine Card; IndustryPacks (VITA 4), the GreenSpring Computers Mezzanine modules; etc. Examples of daughterboard-style expansion cards include: Enhanced Graphics Adapter piggyback board, adds memory beyond 64 KB, up to 256 KB Expanded memory piggyback board, adds additional memory to some EMS and EEMS boards ADD daughterboard RAID daughterboard Network interface controller (NIC) daughterboard CPU Socket daughterboard Bluetooth daughterboard Modem daughterboard AD/DA/DIO daughter-card Communication daughterboard (CDC) Server Management daughterboard (SMDC) Serial ATA connector daughterboard Robotic daughterboard Access control List daughterboard Arduino "shield" daughterboards Beaglebone "cape" daughterboard Raspberry Pi "HAT add-on board" Network Daughterboard (NDB). Commonly integrates: bus interfaces logic, LLC, PHY and Magnetics onto a single board. Standards PCI Extended (PCI-X) PCI Express (PCIe) Mini PCIe M.2 Accelerated Graphics Port (AGP) Peripheral Component Interconnect (PCI) Industry Standard Architecture (ISA) Micro Channel architecture (MCA) VESA Local Bus (VLB) CardBus/PC