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base:efficient_tod_initialisation

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base:efficient_tod_initialisation [2019-05-20 11:45]
silverdr [Proper solution]
base:efficient_tod_initialisation [2020-01-31 17:49] (current)
silverdr [Proper solution]
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   * Short and fast   * Short and fast
  
-Please also note that we use CIA #2 and not CIA #1. CIA #2 is chosen because ​changing the timer values there does not affect regular IRQ timings. MoreoverKERNAL ​re-initialises those timers whenever it wants to use them. This saves as a few bytes, which would otherwise be needed to save and restore timer registers' ​original ​values. Last and least we do not disable NMIs as it is assumed that checking/​setting the params will be done as part of application initialisation,​ before ​setting up IRQ/NMI handlers.+Please also note that we use CIA #2 and not CIA #1. CIA #2 is chosen because ​it timers are by default ​not used by the system. Moreover KERNAL initialises those timers ​according to its needs, ​whenever it wants to use them. This saves us a few bytes, which would otherwise be needed to preserve ​original ​settings. Last and least we do not disable NMIs as it is assumed that checking/​setting the params will be done as part of application initialisation,​ before ​any IRQ/NMI handlers ​are set.
 ===== Dual purpose ===== ===== Dual purpose =====
 I mentioned before that this routine can serve also another purpose and give us potentially even more savings. Yes, with addition of only a few bytes: I mentioned before that this routine can serve also another purpose and give us potentially even more savings. Yes, with addition of only a few bytes:
base/efficient_tod_initialisation.txt ยท Last modified: 2020-01-31 17:49 by silverdr