International Business Machines Corporation

Oliver M Maurel

Philippe Klein

Philippe Cuny

Jean L Calvignac

Bernard J Naudin

Jean-Pierre Lips

The arbitrating method is based on the classification of the users into different categories, and the assignment to all users in a category of an identical privilege level which characterizes the interruption capability of the users in the category. A task performed by a selected user in a category can only be interrupted for granting access to the resource to a user in a category having a higher privilege level. Also a normal preference level is assigned to each user within a category, which determines the selection order of the users in the category. The privilege level of a user category combined with the preference level of each user constitutes the priority level of the user. The access to the resource is granted to a selected user having the highest priority level. If at least one user having a privilege level higher than the privilege level of the selected user, makes a request for the resource, the task of the selected user is interrupted and the interrupted user is assigned an interruption preference level which is higher than the normal preference levels of all other users in the category. A new user having the highest priority level is then selected after the resource is released by the interrupting user.

System for reassigning a higher priority to an interrupted user by

Synchronization apparatus in interconnected units of a data processing system resynchronize received bits from a bus with the internal clock of the unit. The synchronization arrangement has two identical synchonization devices which alternately process received strobe pulses which are used for sampling data bits into a first register, generating a gating pulse on one output and a validation pulse on a second output. In response to the gating pulse, bits stored in the first register are transferred to a second register to be available for use by processing logic in synchronism with the internal clock signal. The synchronization devices include two parallel synchronization circuits operating in opposite phase so that the detection of one strobe pulse by one circuit: automatically disables the other one.

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Le Cannet, France

Oliver M Maurel