Abstract: This invention relates to personal computer systems and, more particularly, to such a system having security features enabling control over access to data retained in such a system. The present invention protects a trusted personal computer system against a probing attack, in which an unauthorized user would attempt to overcome the security feature elements of the personal computer system by inserting some form of probe into an opening provided in the system enclosure for other, legitimate, purposes such as cooling air flow or removable media insertion. A plurality of security feature elements are mounted within the enclosure for selective activation to secure and non-secure states and are disposed at locations inaccessible to any unauthorized user of the personal computer system attempting to affect the operation of any one of the security feature elements by insertion of a probe through an opening.

Abstract: A computer system having a peripheral bus and a digital signal processor (DSP) local bus interfacing to the peripheral bus via an extended bus interface circuit (EBIC). The DSP local bus is configured such that devices, which are typically two or more DSPs, electrically connected to the DSP local bus may transfer data to other devices connected to the DSP local bus regardless of data transfer activity of the peripheral bus. Moreover, as seen from the peripheral bus, the devices connected to the DSP local bus have the same arbitration level. However, as seen from the DSP local bus, each device connected to the DSP local bus has a unique arbitration level determined by the priority of the tasks executing on the respective devices, as determined by a DSP operating system.