From eebdcf85cbadefcaee9521d7bb65dc700de5a22e Mon Sep 17 00:00:00 2001
From: nerd73 <nerd7b@gmail.com>
Date: Sun, 17 May 2020 19:28:40 -0600
Subject: [PATCH] Made writing to MSR 0x8B GPF on Intel Pentium/Pentium MMX

Windows Vista now (correctly) no longer works on these CPUs. IDT WinChip, AMD K6, VIA Cyrix III, and Intel P6 family CPUs are not affected.
---
 src/cpu_common/cpu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/cpu_common/cpu.c b/src/cpu_common/cpu.c
index 0c643f9d9..8e88e9f4b 100644
--- a/src/cpu_common/cpu.c
+++ b/src/cpu_common/cpu.c
@@ -3149,6 +3149,10 @@ void cpu_WRMSR()
                         case 0x10:
 				tsc = EAX | ((uint64_t)EDX << 32);
 				break;
+                        case 0x8B:
+				cpu_log("WRMSR: Invalid MSR: 0x8B/n"); /*Needed for Vista to correctly break on Pentium*/
+				x86gpf(NULL, 0);
+				break;
                 }
                 break;
 #if defined(DEV_BRANCH) && defined(USE_CYRIX_6X86)