Starting from [3548] the driver performs very slow (~100Kb) after some time. 100% way to force it into this "mode" is to force rate 54M, then auto with iwconfig. [3547] driver works OK - ~17Mb of actual throughout as measured by iperf.
dmesg from working driver:
ath_pci: svn r3546
PCI: Enabling device 0000:06:00.0 (0000 -> 0002)
ACPI: PCI Interrupt 0000:06:00.0[A] -> Link [LNKB] -> GSI 11 (level, low) -> IRQ 11
MadWifi: ath_attach: HAL managed transmit power control (TPC) disabled.
MadWifi: ath_attach: Interference mitigation is supported. Currently disabled.
MadWifi: ath_attach: Switching rfkill capability off.
ath_rate_sample: 1.2 (svn r3546)
wifi0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
wifi0: 11g rates: 1Mbps 2Mbps 5.5Mbps 11Mbps 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps
wifi0: turboG rates: 6Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps
wifi0: H/W encryption support: WEP AES AES_CCM TKIP
wifi0: ath_announce: Use hw queue 1 for WME_AC_BE traffic
wifi0: ath_announce: Use hw queue 0 for WME_AC_BK traffic
wifi0: ath_announce: Use hw queue 2 for WME_AC_VI traffic
wifi0: ath_announce: Use hw queue 3 for WME_AC_VO traffic
wifi0: ath_announce: Use hw queue 8 for CAB traffic
wifi0: ath_announce: Use hw queue 9 for beacons
ath_pci: wifi0: Atheros 5212: mem=0x3c000000, irq=11