Hardware Overview

The Atheros 802.11 NIC is, at it's core, a DMA engine with hardware timers implementing the 802.11 packet timing. The hardware handles doing the OFDM/CCK RF encoding and decoding.

General Overview

The NIC can be broken down into a few larger blocks:

There's more going on internally. (TODO: go dumpster diving through the Atheros patents to look for hardware descriptions.)


The MAC side is further broken down into:

The MAC itself implements (not an exhaustive list!):


The PHY implements the packet encoding and decoding. The MAC selects packets to send to the PHY for transmission; the PHY decodes packets from the air and sends them to the MAC for reception. (Yes, the Atheros NIC drivers do no actual packet encoding/decoding in software - the hardware does all of this. It's not a software defined radio.)

It is also responsible for watching the air and determining when the air is clear enough to transmit. The MAC has an input (RX_CLEAR) which it uses to determine whether it's able to transmit or not.

The PHY has one (or more, for later chips) ADCs and DACs which handle receiving and transmitting encoding frames to the analog section.


The Analog section links into the PHY via the ADCs and DACs. It's responsible for tuning to the relevant 2 or 5GHz frequency and converting things as needed.

Chipset specifics


The MAC supports:

The AR5210 requires an external analog chip (RF5110) which handles the 5GHz conversion.


The AR5211 MAC supports:

The AR5211 requires an external analog chip. There were two made: RF5111 for 5GHz operation and RF2111 for 2GHz operation. The driver would configure which analog chip was active.

Since the decoder can't automatically determine the difference between OFDM and CCK on received frames, the AR5211 doesn't support 802.11bg operation. It either supports 802.11b operation (CCK) or 802.11g operation (OFDM) or 802.11a operation (OFDM). This is why madwifi/net80211 supported the concept of "PUREG" - OFDM-only in 2GHz.

The AR5212 MAC supports:

The AR5212 is the first to support automatic OFDM/CCK detection on received packets. This allows it to operate as an 802.11bg aware device (ie, OFDM and CCK on a 2GHz channel.)

The 10 TX queues allow for separate WMM parameters for each of the 8 WMM QoS levels.

AR5416 and later 802.11n NICs



The AR7010 isn't a wireless device - it's a Tensilica core with a USB, Ethernet and PCIe to connect to various devices. The most popular core - AR7010 - has a USB target mode interface, a PCIe interface to connect to an Atheros wireless NIC, and onboard RAM/flash. Other options were available (Ethernet, PCIe to connect to the host.)


The AR9271 can be viewed as an AR7010 style device with an AR9285 NIC on-die.

See also

dev/ath_hal(4)/HardwareOverview (last edited 2013-09-19T20:20:42+0000 by AdrianChadd)