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Some timer tweaks to improve run repeatability

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This commit is contained in:
Jeff Parsons 2014-11-23 16:57:35 -08:00 • committed by jeffpar
commit 35237a637b
3 changed files with 86 additions and 118 deletions
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38
modules/pcjs/lib/cpu.js
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@ -574,24 +574,6 @@ CPU.prototype.setBurstCycles = function(nCycles)
return false;
};
/**
* setBurstDivisor(nDivisor)
*
* This is called by the ChipSet component, on behalf of TIMER0, whenever the initial timer count has been
* reprogrammed to a lower-than-default value, requiring the CPU to perform more frequent timer updates.
*
* A divisor greater than 1 (the default) does NOT require us to yield more frequently or update the screen
* more frequently; it only means that stepCPU() must be called more frequently, with correspondingly smaller burst
* cycles, because stepCPU() is responsible for updating all the timers ONCE, each time it's called.
*
* @this {CPU}
* @param {number} nDivisor
*/
CPU.prototype.setBurstDivisor = function(nDivisor)
{
this.nBurstDivisor = nDivisor;
};
/**
* addCycles(nCycles, fEndStep)
*
@ -737,7 +719,6 @@ CPU.prototype.getCyclesPerSecond = function()
CPU.prototype.resetCycles = function()
{
this.aCounts.mhz = 0;
this.setBurstDivisor(1);
this.nTotalCycles = this.nRunCycles = this.nBurstCycles = this.nStepCycles = 0;
this.resetChecksum();
this.setSpeed(1);
@ -986,20 +967,13 @@ CPU.prototype.runCPU = function(fOnClick)
this.calcStartTime();
try {
do {
var nCyclesPerBurst = this.aFlags.fChecksum? 1 : Math.round(this.aCounts.nCyclesPerBurst / this.nBurstDivisor);
var nCyclesPerBurst = (this.aFlags.fChecksum? 1 : this.aCounts.nCyclesPerBurst);
/*
* This is an alternative to ChipSet calling setBurstDivisor(). Unfortunately, this doesn't seem
* to work as well as setBurstDivisor(); for some reason, the smaller bursts that the burst divisor
* produces results in smoother video updates (see "BASICA DONKEY.BAS"). TODO: Research required;
* be sure to disable the setBurstDivisor() code in chipset.js if you enable this code.
*
* var nCyclesTimer0 = (this.chipset? (this.chipset.getTimerCycleLimit(0)): 0);
* if (nCyclesTimer0 && nCyclesPerBurst > nCyclesTimer0) {
* nCyclesPerBurst = nCyclesTimer0;
* }
*/
if (this.chipset) nCyclesPerBurst = this.chipset.getRTCCycleLimit(nCyclesPerBurst);
if (this.chipset) {
this.chipset.updateAllTimers();
nCyclesPerBurst = this.chipset.getTimerCycleLimit(0, nCyclesPerBurst);
nCyclesPerBurst = this.chipset.getRTCCycleLimit(nCyclesPerBurst);
}
/*
* nCyclesPerBurst is how many cycles we WANT to run on each iteration of stepCPU(), but it may run