Common Design Patterns for Symbian OS: The Foundations of Smartphone Software

Appendix A. Impact Analysis of Recurring Consequences

This appendix analyzes the impact of consequences that recur in the patterns described in this book. Note that the data given here is only intended to allow you to assess the feasibility of design decisions and should not be taken as accurate figures to be precisely relied upon. We recommend that you measure directly any facts on which you base the development of your software.

In this discussion, the following factors can make a significant difference to the impact of using a pattern:

• which type of CPU is present on the device

• which memory model is being used: this is determined by the CPU;^[] ARMv5 usually implies the moving memory model whilst ARMv6 usually implies the multiple memory model

  ^[] This may be listed on the device manufacturer's website, e.g. for S60 devices: www.forum.nokia.com/devices.

• whether code is eXecuted In Place (XIP) or not (non-XIP).

At the time of writing, the most common device configuration is an ARMv6 core with non-XIP flash. However, older or midrange devices may well use an ARMv5 core with either XIP or non-XIP flash.

See also [Sales, 2005] as this provides helpful background material to the discussion here.