The ebuild for at76c503a originally written for X86 has been tested on AMD64 and works without modification to the original ebuild. Reproducible: Always Steps to Reproduce: 1. 2. 3.
Created attachment 49835 [details] ebuild for at76c503a
I'm happy to report that this driver works fine for me under amd64. I'm currently downloading at over 100K/s from Oracle using it. I have a Belkin F5D6050 which is an at76c503 chipset, and dual am64 cpus. The only small caveat is that some comments at the end of the build to point out that the configuration is made persistent in /etc/conf.d/wireless and you need to create a file net.wlan0 in /etc/init.d would have saved a bit of time.
i marked it testing yesterday or so