AMR, CNR and ACR slots
By Gabriel Torres on October 23, 2004


Introduction

AMR (Audio Modem Riser), CNR (Communications and Network Riser) and ACR (Advanced Communications Riser) are slots that you can find on your motherboard that have the same goal: to install HSP (Host Signal Processing) devices to your PC. These devices can be modems, sound cards and network cards.

HSP devices lack self-control, it is the computer CPU that controls the device. As a result, the device is fairly cheap, because it doesn't have any fancy circuitry. But, on the other hand, the PC loses a little bit of its performance, since the processor will waste a little bit of its time controlling the device. This kind of device is also commonly refered as "software-controlled" (e.g., "soft modems").

Usually AMR, CNR and ACR devices are offered by the motherboard manufacturer as an option to the motherboard. For example, your motherboard can have a AMR modem as an option. You can also buy such devices on the market. An AMR modem costs USD 15 or less, but they are not so easy to find.

You will only find one of these slots at a time, i.e., if a motherboard has AMR slot, you won't find a CNR nor an ACR slot on it.

Let's take a look at the physical differences between these slots.

AMR (Audio Modem Riser)

The AMR slot can be found in the middle of the motherboard, besides the AGP slot.

AMR slot
click to enlarge
Figure 1: AMR slot location.

AMR Modem
click to enlarge
Figure 2: Example of an AMR modem.

AMR slot
click to enlarge
Figure 3: AMR modem installed on the motherboard.

CNR (Communications and Network Riser)

The CNR slot is located on the side of the motherboard, near the last PCI slot. As you can see comparing Figures 1 and 4, AMR and CNR devices are a little bit different, event though the slots are very similar. Not only the edge connector (the part that goes into the slot) is different, the card has a different orientation. The side that has the I/O connectors on an AMR device is located to the left, and this side on a CNR device is located to the right.

CNR slot
click to enlarge
Figure 4: CNR slot location.

CNR modem
Figure 5: Example of a CNR modem.

ACR (Advanced Communications Riser)

This slot was created by ASUS and you will find it only on motherboards from this manufacturer. Physically it is very different from AMR and CNR, because this slot is the same used by the PCI bus, but rotated 180 degrees. So, it is white (CNR and AMR are usually brown) and bigger than the previous slots we've seen. It is located at the same place as the CNR slot: at the motherboard side, besides the last PCI slot.

ACR slot
click to enlarge
Figure 6: ACR slot location.

ACR Audio Card
Figure 7: Example of an ACR audio card.

Originally at http://www.hardwaresecrets.com/article/AMR-CNR-and-ACR-slots/46


2004-13, Hardware Secrets, LLC. All Rights Reserved.

Total or partial reproduction of the contents of this site, as well as that of the texts available for downloading, be this in the electronic media, in print, or any other form of distribution, is expressly forbidden. Those who do not comply with these copyright laws will be indicted and punished according to the International Copyrights Law.

We do not take responsibility for material damage of any kind caused by the use of information contained in Hardware Secrets.