To calculate the theoretic throughput of the PCI bus, use the following formula:
( bit * Hz ) / (1024 * 1024 * 8 ) = Throughput in MByte/s
On average the throughput will be 10 to 20 MByte/s more than this theoretical value.
For example, a 64bit PCI bus at 66MHz: ( 64 * 66.000.000 ) / ( 1024 * 1024 * 8 ) = 503,54 MByte/s
Other specs: http://www.sci.hkbu.edu.hk/hpccc/hardware_specification.php