1. Apparatus for determining a memory configuration of memory modules for use in controlling said memory modules, each of said memory modules producing presence detect bits, comprising: an external register for receiving said presence detect bits from each of said memory modules in parallel and for storing said presence detect bits, said presence detect bits including encoded bits representative of memory module capacity and memory module speed; a memory controller integrated circuit for controlling said memory modules, said external register being located external to said memory controller integrated circuit, said memory controller integrated circuit including an internal register for storing said presence detect bits; means for serially transferring said presence detect bits from said external register to said internal register; and logic means within said memory controller integrated circuit for determining a memory configuration in response to said presence detect bits.