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ST7 AND ST9 PERFORMANCE BENCHMARKING

4 RESULT ANALYSIS

This section is an analysis of computing performance and interrupt processing

performance results (for execution time and code size). Based on core architecture analysis

(see section 7), two comparisons are presented, pointing out the strong and weak points of

each MCU. The first concerns the high-end to medium-end MCUs versus ST9+. The

second concerns the medium-end to low-end MCUs versus ST7.

4.1 PRELIMINARY REMARK

Results show that the two different ratios, for execution time and code size, calculated with full

and reduced sets of tests, are in fact not very different. In most cases, the classification of the

MCUs is kept. Thus we can consider that the reduced set is sufficient to make the MCU

core comparison.

4.2 HIGH-END TO MEDIUM-END MCU ANALYSIS VERSUS ST9+

The Table 3 presents the strong and the weak points for high-end to medium-end MCUs,

compared to the ST9+ MCU.

Notes: ICT means Instruction Cycle Time and IL means Instruction Length.

Refer to paragraph <Italic>7.2.2 Average ICT/CPI and IL<Italic end> for details on

calculation.

Refer to paragraph <Italic>7.3.4 ST9+ MCU core<Italic end> to see the main characteristics of

the ST9+ MCU core.

4.2.1 Computing performance results

Regarding speed, the ST9+ MCU ranks at the top of 8/16-bit MCUs. This new version of the

ST9 has been improved on several points, including clock per instruction and clock speed.

These enhancements have considerably reduced its instruction cycle time. A large and

powerful register file organized in groups allow the ST9+ to perform strong computation

(with many registers), have an easy access to peripheral and i/o port registers (with paged

registers), and manage multitasking (with register group pointers). Addressing modes like

perform 16-bit data computation and manipulation, easily manipulate tables and move

blocks. A new memory management unit enlarges the memory space up to 4 Mbytes. New

instructions have been added to handle this new space and improve the C-language

support.

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