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genesis: reduce CPU usage

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the chip uses TDM to output the channels one by one
so we just run the chip 6 times and output at 1/6th the rate, which
means less work for blip_buf and less C++ overhead
This commit is contained in:
tildearrow 2021-06-09 01:57:12 -05:00
parent cf6b213d2c
commit b30c5679ae
1 changed files with 15 additions and 7 deletions
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22
src/engine/platform/genesis.cpp
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@ -14,9 +14,11 @@ static unsigned char konOffs[6]={
void DivPlatformGenesis::acquire(int& l, int& r) {
static short o[2];
static int os[2];
if (dacMode && dacSample!=-1) {
if (--dacPeriod<1) {
dacPeriod-=6;
if (dacPeriod<1) {
DivSample* s=parent->song.sample[dacSample];
if (s->depth==8) {
writes.emplace(0x2a,(unsigned char)s->rendData[dacPos++]+0x80);
@ -26,7 +28,7 @@ void DivPlatformGenesis::acquire(int& l, int& r) {
if (dacPos>=s->rendLength) {
dacSample=-1;
}
dacPeriod=dacRate;
dacPeriod+=dacRate;
}
}
@ -47,18 +49,24 @@ void DivPlatformGenesis::acquire(int& l, int& r) {
}
}
}
OPN2_Clock(&fm,o);
os[0]=0; os[1]=0;
OPN2_Clock(&fm,o); os[0]+=o[0]; os[1]+=o[1];
OPN2_Clock(&fm,o); os[0]+=o[0]; os[1]+=o[1];
OPN2_Clock(&fm,o); os[0]+=o[0]; os[1]+=o[1];
OPN2_Clock(&fm,o); os[0]+=o[0]; os[1]+=o[1];
OPN2_Clock(&fm,o); os[0]+=o[0]; os[1]+=o[1];
OPN2_Clock(&fm,o); os[0]+=o[0]; os[1]+=o[1];
//OPN2_Write(&fm,0,0);
psgClocks+=223722;
if (psgClocks>=rate) {
while (psgClocks>=rate) {
psg.acquire(psgOut,psgOut);
psgClocks-=rate;
psgOut=(psgOut>>2)+(psgOut>>3);
}
l=(o[0]<<7)+psgOut;
r=(o[1]<<7)+psgOut;
l=(os[0]<<5)+psgOut;
r=(os[1]<<5)+psgOut;
}
void DivPlatformGenesis::tick() {
@ -333,7 +341,7 @@ int DivPlatformGenesis::dispatch(DivCommand c) {
int DivPlatformGenesis::init(DivEngine* p, int channels, int sugRate) {
parent=p;
rate=1278409;
rate=213068;
OPN2_Reset(&fm);
for (int i=0; i<10; i++) {
chan[i].vol=0x7f;