An approach to microprogram optimization considering resource occupancy and instruction formats

Abstract

This paper describes a microprogram optimization technique considering resource occupancy and microinstruction format. This technique is applicable to machines whose microoperation occupies several machine cycles on a submachine cycle basis, and whose microinstruction format varies from horizontal to partially encoded, to vertical. “Microtemplate” is proposed to represent fetch timing and period of resource usage for a microoperation on a machine cycle and submachine cycle basis. An algorithm is shown, which detects concurrency of sequentially written microoperations through manipulation of microtemplates. An algorithm of microinstruction format selection is also discussed which decides one instruction format when several candidates exist. Effectiveness of this technique is evaluated. Efficient object codes are generated when applied to a practical sophisticated microprogrammable computer.