From 2063303a4d981c7d8f15cd38e59fce3214a3421b Mon Sep 17 00:00:00 2001
From: gm-matthew <108370479+gm-matthew@users.noreply.github.com>
Date: Tue, 22 Nov 2022 01:43:38 +0000
Subject: [PATCH] Wait until IRQ2 is acknowledged before starting IRQ40
 sequence. Fixes Ski Champ hanging at FBI screen when region set to USA

---
 Src/Model3/Model3.cpp | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/Src/Model3/Model3.cpp b/Src/Model3/Model3.cpp
index ca2e7ce..bff690e 100644
--- a/Src/Model3/Model3.cpp
+++ b/Src/Model3/Model3.cpp
@@ -2041,10 +2041,9 @@ void CModel3::RunMainBoardFrame(void)
 	// Compute display and VBlank timings
 	unsigned ppcCycles		= m_config["PowerPCFrequency"].ValueAs<unsigned>() * 1000000;
 	unsigned frameCycles	= (unsigned)((float)ppcCycles / 57.524160f);
-	unsigned gapCycles		= (unsigned)((float)frameCycles * 2.5f / 100.0f);	// we need a gap between asserting irq2 & irq 0x40
-	unsigned offsetCycles = (unsigned)((float)frameCycles * 33.f / 100.0f);
-	unsigned dispCycles		= frameCycles - gapCycles - offsetCycles;
-	unsigned statusCycles = (unsigned)((float)frameCycles * (0.005f));
+	unsigned offsetCycles   = (unsigned)((float)frameCycles * 33.f / 100.0f);
+    unsigned dispCycles     = frameCycles - offsetCycles;
+	unsigned statusCycles   = (unsigned)((float)frameCycles * (0.005f));
 
 	// we think a frame looks like this on the model 2
 	//                         66% of frame
@@ -2069,7 +2068,13 @@ void CModel3::RunMainBoardFrame(void)
 
 		ppc_execute(offsetCycles);
 		IRQ.Assert(0x02);								// start at 33% of the frame
-		ppc_execute(gapCycles);					// need a gap between asserting irqs
+
+        // keep running cycles until IRQ2 is acknowledged
+        while (IRQ.ReadIRQEnable() & 0x2 && IRQ.ReadIRQState() & 0x2 && dispCycles > 1000)
+        {
+            ppc_execute(1000);
+            dispCycles -= 1000;
+        }
 
 		/*
 		* Sound: