A Partitioning Example

Partitioning results are given here for the IBM System/370. Other partitioning results are presented in Chapter RESULTS. 

Behavioral transformations were run on the System/370 VT to eliminate unnecessary operators, combine SELECT operators where possible, and inline expand any vtbodies that are only called once. This resulted in one large vtbody containing the gist of the instructions, and a number of smaller vtbodies containing auxiliary functions. 

A research effort at IBM studied methods of partitioning the System/370 [Agnew82]. Instructions set partitioning was chosen as the best general method of partitioning primarily because of the reduced number of control breaks necessary with that partitioning scheme, and because it allows the partitions to be implemented on off-the-shelf microprocessors (Motorola s 68000). Seven instruction set partitioning schemes are described in the article that summarizes this research. APARTY s ability to address the various schemes is described below. 

Among the three remaining partitioning schemes for the System/370, the partitions can be described in terms of 5 functional groups the instruction fetch cycle for all instructions the execution cycles for fixed point, load/store and branch instructions the execution cycles for floating point instructions the execution cycles for privileged instructions and the execution cycles for decimal instructions. These groups are combined in various ways to make up the three schemes. 

This result indicates that APARTY is capable of addressing instruction set partitions, and makes reasonable choices of instruction groups in order to reduce data dependencies between the instruction subsets. 

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