From 5664e81d48dd932f2545498d844ae14330ccbcc9 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 18 Mar 2021 12:41:24 -0400
Subject: [PATCH] It appears the +2a and +3 have a different clock rate.

---
 Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp | 24 +++++++++++++++------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp b/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
index cf9e00556..8ca2ce2f3 100644
--- a/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
+++ b/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
@@ -26,10 +26,6 @@
 
 #include <array>
 
-namespace {
-	const unsigned int ClockRate = 3'500'000;
-}
-
 
 namespace Sinclair {
 namespace ZXSpectrum {
@@ -48,8 +44,8 @@ template<Model model> class ConcreteMachine:
 			mixer_(ay_, audio_toggle_),
 			speaker_(mixer_)
 		{
-			set_clock_rate(ClockRate);
-			speaker_.set_input_rate(float(ClockRate) / 2.0f);
+			set_clock_rate(clock_rate());
+			speaker_.set_input_rate(float(clock_rate()) / 2.0f);
 
 			// With only the +2a and +3 currently supported, the +3 ROM is always
 			// the one required.
@@ -69,6 +65,12 @@ template<Model model> class ConcreteMachine:
 			audio_queue_.flush();
 		}
 
+		static constexpr unsigned int clock_rate() {
+//			constexpr unsigned int ClockRate = 3'500'000;
+			constexpr unsigned int Plus3ClockRate = 3'546'900;
+			return Plus3ClockRate;
+		}
+
 		// MARK: - TimedMachine
 
 		void run_for(const Cycles cycles) override {
@@ -114,8 +116,8 @@ template<Model model> class ConcreteMachine:
 				break;
 
 				case PartialMachineCycle::Output:
+					// Test for port FE.
 					if(!(address&1)) {
-						// TODO: rest of port FE.
 						update_audio();
 						audio_toggle_.set_output(*cycle.value & 0x10);
 
@@ -124,6 +126,14 @@ template<Model model> class ConcreteMachine:
 						// b4: tape and speaker output
 					}
 
+					// Test for classic 128kb paging.
+//					if(!(address&0x8002)) {
+//					}
+
+					// Test for +2a/+3 paging.
+//					if((address & 0xc002) == 0x4000) {
+//					}
+
 					switch(address) {
 						default: break;