IOGear 802.11g WiFi card happens in two flavors. Earlier version (I’ll call it v1) has ISL3880 chip and is fully¹ supported by recent kernels (18.104.22.168 at least). Later version (v2) has GW3887 chip and would (will) be supported by the vanilla kernel¹, but its id is not added to the driver configuration.
To check if you have older or newer card you can use lsusb command. 124A:4023 is v1, while 124a:4025 is newer v2.
¹ Kernel driver needs an external firmware called SoftMAC to run. It is available from Prism Firmwares site. More information can be also obtained at http://prism54.org/ (except that as of now neither mention newer GWU 513 card at all).
So to make v2 GWU513 card work, you need to:
- patch the kernel with add a 124a:4025 id patch and recompile it
- download the “Second generation device” firmware 22.214.171.124 (for v1 it would be “First generation device”, 126.96.36.199)
- put it in appropriate place at appropriate name in the system (on mine Fedora 8 it is /lib/firmware/isl3887usb_bare)
- load/reload p54usb kernel module (i.e. rmmod p54usb; modprobe p54usb)
- iwconfig should show the new card
Post Scriptum: this is an import of information that I wrote a while ago. Things might have changed since then.