From ee982d5754b68e28d9b355ec1f8cb9f38c85260d Mon Sep 17 00:00:00 2001
From: Peter Veenstra <qbix79@users.sourceforge.net>
Date: Tue, 30 Aug 2011 13:15:36 +0000
Subject: [PATCH] Use a fixed cycle rate in auto cycles mode when calculating
 RDTSC. Improves Tie break Tennis 98

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3748
---
 src/cpu/core_full/load.h        | 2 +-
 src/cpu/core_normal/prefix_0f.h | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/cpu/core_full/load.h b/src/cpu/core_full/load.h
index cd620add..0a3f1ae0 100644
--- a/src/cpu/core_full/load.h
+++ b/src/cpu/core_full/load.h
@@ -502,7 +502,7 @@ l_M_Ed:
 		continue;
 	case D_RDTSC: {
 		if (CPU_ArchitectureType<CPU_ARCHTYPE_PENTIUMSLOW) goto illegalopcode;
-		Bit64s tsc=(Bit64s)(PIC_FullIndex()*(double)CPU_CycleMax);
+		Bit64s tsc=(Bit64s)(PIC_FullIndex()*(double)(CPU_CycleAutoAdjust?70000:CPU_CycleMax));
 		reg_edx=(Bit32u)(tsc>>32);
 		reg_eax=(Bit32u)(tsc&0xffffffff);
 		break;
diff --git a/src/cpu/core_normal/prefix_0f.h b/src/cpu/core_normal/prefix_0f.h
index 84f1b741..38004f1f 100644
--- a/src/cpu/core_normal/prefix_0f.h
+++ b/src/cpu/core_normal/prefix_0f.h
@@ -228,7 +228,8 @@
 	CASE_0F_B(0x31)												/* RDTSC */
 		{
 			if (CPU_ArchitectureType<CPU_ARCHTYPE_PENTIUMSLOW) goto illegal_opcode;
-			Bit64s tsc=(Bit64s)(PIC_FullIndex()*(double)CPU_CycleMax);
+			/* Use a fixed number when in auto cycles mode as else the reported value changes constantly */
+			Bit64s tsc=(Bit64s)(PIC_FullIndex()*(double) (CPU_CycleAutoAdjust?70000:CPU_CycleMax));
 			reg_edx=(Bit32u)(tsc>>32);
 			reg_eax=(Bit32u)(tsc&0xffffffff);
 		}