From 60058283ebaa0e92de398602a110eb9391df7185 Mon Sep 17 00:00:00 2001
From: SarahW <pcem@pcem-emulator.co.uk>
Date: Fri, 17 May 2019 20:15:09 +0100
Subject: [PATCH] Disable FDC when enabling W83877TF config registers at 0x3f0,
 to prevent bus conflicts. Fixes duplicate FDC/COM/LPT ports on VA-503+.

---
 src/w83877tf.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/w83877tf.c b/src/w83877tf.c
index 78c2a63..17e80f1 100644
--- a/src/w83877tf.c
+++ b/src/w83877tf.c
@@ -138,12 +138,21 @@ static void w83877tf_write_3fx(uint16_t port, uint8_t val, void *p)
         {
                 case 0x3f0: /*Enable/index register*/
                 if (val == 0xaa)
+                {
+                        fdc_remove();
+                        if (w83877tf->enable_regs && w83877tf->regs[0x20] >= 0x40)
+                                fdc_add();
                         w83877tf->enable_regs = 0;
+                }
                 else if (!w83877tf->enable_regs)
                 {
                         w83877tf->key[1] = w83877tf->key[0];
                         w83877tf->key[0] = val;
                         w83877tf->enable_regs = (w83877tf->key[0] == 0x87 && w83877tf->key[1] == 0x87);
+                        /*The FDC conflicts with the 3fx config registers, so disable
+                          it when enabling config registers*/
+                        if (w83877tf->enable_regs)
+                                fdc_remove();
                 }
                 else
                         w83877tf->index = val;