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An audio modem riser (AMR) is a short riser expansion slot on the motherboard of certain Intel PCs such as Pentium III and IV. Its availability is also visible in AMD Athlon and AMD Duron PCs. The audio modem riser is designed as an easy and inexpensive way to incorporate special sound cards and modems into a system. The AMR slot was first introduced by Intel in 1998 as a way to allow motherboard manufacturers to use an analog input/output (I/O) system for audio and modem functions on an expansion board.
Also known as an AMR slot.
The AMR was designed to decrease the cost of a computer system in several ways:
The AMR has a total of 46 pins, arranged in two rows of 23 pins each. It uses analog I/O audio functions that require a software driver and a modem circuitry loaded with a codec chip to translate analog and digital signals. The small riser board fits directly into the motherboard.
It is called a riser board because it does not lay flat on the motherboard but rises above it.
The AMR provided a way to add advanced audio and modem design at minimal cost thus allowing manufacturers to design custom systems. At the same time, motherboards did not have built-in audio and modem functionalities. However, although the AMR basically replaced the PCI slot, many original equipment manufacturers did not want to use it because it had limited abilities such as no plug-n-play.
The AMR slot was superseded by the communications and networking riser (CNR) and the advanced communications riser (ACR), which also became obsolete. Then technology took a different turn, using audio interfaces incorporated directly onto the motherboard, while modems continued to use PCI slots. However, there is a high-definition multimedia riser (HDMR) slot developed by Asrock, which is used for the HDMR card that has v92 modem functions.