The primary driver for all Ettus Research products - including the USRP1 - is UHD, the Universal Hardware Driver. UHD software is considered stable and is actively maintained by Ettus Research.
The schematics for all Ettus Research products, including the USRP and USRP2 devices, and all daughterboards are available here:
- USRPClockingNotes has info about using external clocks with the USRP1 device
- USRPSerialBelow500 instructions on how to send the USRP clock to the daughterboards, for USRP devices with a serial number below 500
- FPGA including details of USB interface along with RX and TX chains