A serial bus and connection to a device on a computer system through a system memory controller is provided on a memory card having a DSP and a memory bus controller to allow the DSP on the memory card to gain access to the system device without using the system memory bus. The serial bus is a two wire serial bus connecting the device to the DSP through the system memory controller. If more than one memory card is present with DSPs or more than one device is contending for access, the system memory controller or arbitrate the access of each memory card or contending device. In such case the serial bus will signal the system memory controller when it wants access to the particular device, and the system memory controller will act as arbitrator to grant or not grant access to the particular memory card or device requesting access. If access is granted the bus memory controller outputs the required control or command word on the serial bus followed by the address and the required data. This serial information is received by the system memory controller which packets it, and, upon completion, outputs the information rapidly on a parallel bus, e.g. a PCI bus to the device which needs the information.