Advanced Communications Riser
The ACR specification provides a lower cost method to connect certain expansion cards to a computer, with an emphasis on audio and communications devices. sound cards and modems are the most common devices to use the specification. ACR and other riser cards lower hardware costs by offloading much of the computing tasks of the peripheral to the CPU
ACR uses a 120 pin PCI connector which is reversed and offset, retaining backward compatibility with 46 pin AMR cards while including support for newer technologies. These new features include standards for an EEPROM for storing model and vendor information, USB support, and the Integrated Packet Bus for DSL, cable modem, and wireless networking support
The ACR specification was created by the Advanced Communications Riser Special Interest Group (ACR SIG) in 2000 with the intent to replace the AMR specification. Because it was backwards compatible with AMR cards, and technically superior, it quickly replaced it.