From 9d2dd22d6d68c8347408bb8f1f3650457e644520 Mon Sep 17 00:00:00 2001
From: TomW <TomW@localhost>
Date: Mon, 12 Oct 2015 13:42:09 +0100
Subject: [PATCH] Initialise A20 gate correctly at startup. Keyboard controller
 self-test command enables A20. HIMEM.SYS included with Windows/286 now works.

---
 src/keyboard_at.c | 11 ++++++++++-
 src/mem.c         |  8 +++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/keyboard_at.c b/src/keyboard_at.c
index c02f506..4c89a56 100644
--- a/src/keyboard_at.c
+++ b/src/keyboard_at.c
@@ -340,6 +340,15 @@ void keyboard_at_write(uint16_t port, uint8_t val, void *priv)
                         keyboard_at.status |= STAT_SYSFLAG;
                         keyboard_at.mem[0] |= 0x04;
                         keyboard_at_adddata(0x55);
+                        /*Self-test also resets the output port, enabling A20*/
+                        if (!(keyboard_at.output_port & 0x02))
+                        {
+                                mem_a20_key = 2;
+                                mem_a20_recalc();
+//                                pclog("Rammask change to %08X %02X\n", rammask, val & 0x02);
+                                flushmmucache();
+                        }
+                        keyboard_at.output_port = 0xcf;
                         break;
                         
                         case 0xab: /*Interface test*/
@@ -445,7 +454,7 @@ void keyboard_at_reset()
         keyboard_at.status = STAT_LOCK | STAT_CD;
         keyboard_at.mem[0] = 0x11;
         keyboard_at.wantirq = 0;
-        keyboard_at.output_port = 0;
+        keyboard_at.output_port = 0xcf;
         keyboard_at.input_port = 0xb0;
         keyboard_at.out_new = -1;
         keyboard_at.last_irq = 0;
diff --git a/src/mem.c b/src/mem.c
index 16548d6..57c5fd3 100644
--- a/src/mem.c
+++ b/src/mem.c
@@ -1736,6 +1736,9 @@ void mem_add_bios()
         mem_mapping_add(&bios_high_mapping[7], 0xffffc000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x1c000 & biosmask), 0, 0);
 }
 
+int mem_a20_key = 0, mem_a20_alt = 0;
+static int mem_a20_state = 1;
+
 void mem_init()
 {
         int c;
@@ -1847,6 +1850,8 @@ void mem_resize()
         mem_mapping_add(&romext_mapping,  0xc8000, 0x08000, mem_read_romext, mem_read_romextw, mem_read_romextl, NULL, NULL, NULL,   romext, 0, NULL);
 
 //        pclog("Mem resize %i %i\n",mem_size,c);
+        mem_a20_key = 2;
+        mem_a20_recalc();
 }
 
 void mem_reset_page_blocks()
@@ -1863,9 +1868,6 @@ void mem_reset_page_blocks()
         }
 }
 
-int mem_a20_key = 0, mem_a20_alt = 0;
-static int mem_a20_state = 0;
-
 void mem_a20_recalc()
 {
         int state = mem_a20_key | mem_a20_alt;