From 5dac609d92f0c317d9088a00c79b428c5f0eafae Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Sun, 27 Mar 2022 01:47:27 -0500
Subject: [PATCH] Genesis: better DAC write algorithm

only write DAC if there aren't too many queued writes
---
 src/engine/platform/genesis.cpp     | 8 ++++++--
 src/engine/platform/genesisshared.h | 2 +-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/engine/platform/genesis.cpp b/src/engine/platform/genesis.cpp
index 46e24333..10a8762c 100644
--- a/src/engine/platform/genesis.cpp
+++ b/src/engine/platform/genesis.cpp
@@ -92,7 +92,9 @@ void DivPlatformGenesis::acquire_nuked(short* bufL, short* bufR, size_t start, s
         DivSample* s=parent->getSample(dacSample);
         if (s->samples>0) {
           if (!isMuted[5]) {
-            urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+            if (writes.size()<16) {
+              urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+            }
           }
           if (++dacPos>=s->samples) {
             if (s->loopStart>=0 && s->loopStart<(int)s->samples) {
@@ -159,7 +161,9 @@ void DivPlatformGenesis::acquire_ymfm(short* bufL, short* bufR, size_t start, si
         DivSample* s=parent->getSample(dacSample);
         if (s->samples>0) {
           if (!isMuted[5]) {
-            urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+            if (writes.size()<16) {
+              urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+            }
           }
           if (++dacPos>=s->samples) {
             if (s->loopStart>=0 && s->loopStart<(int)s->samples) {
diff --git a/src/engine/platform/genesisshared.h b/src/engine/platform/genesisshared.h
index 6410ddb2..3d5320f6 100644
--- a/src/engine/platform/genesisshared.h
+++ b/src/engine/platform/genesisshared.h
@@ -44,6 +44,6 @@ static int orderedOps[4]={
 
 #define rWrite(a,v) if (!skipRegisterWrites) {pendingWrites[a]=v;}
 #define immWrite(a,v) if (!skipRegisterWrites) {writes.push_back(QueuedWrite(a,v)); if (dumpWrites) {addWrite(a,v);} }
-#define urgentWrite(a,v) if (!skipRegisterWrites) {if (writes.empty() || writes.front().addrOrVal) {writes.push_back(QueuedWrite(a,v));} else {writes.push_front(QueuedWrite(a,v));}; if (dumpWrites) {addWrite(a,v);} }
+#define urgentWrite(a,v) if (!skipRegisterWrites) {if (writes.empty() || writes.size()>16 || writes.front().addrOrVal) {writes.push_back(QueuedWrite(a,v));} else {writes.push_front(QueuedWrite(a,v));}; if (dumpWrites) {addWrite(a,v);} }
 
 #include "fmshared_OPN.h"