From 636e49fd2b8a3b897657412dc2493c978d15173f Mon Sep 17 00:00:00 2001
From: DeaDDooMER <deaddoomer@deadsoftware.ru>
Date: Fri, 17 Aug 2018 23:15:08 +0300
Subject: [PATCH] Now A20 line works

---
 Boot486/boot0.S          | 161 +++++----------------------------------
 Boot486/run.sh           |   2 +-
 System/Mod486/Kernel.odc | Bin 84020 -> 85026 bytes
 3 files changed, 21 insertions(+), 142 deletions(-)

diff --git a/Boot486/boot0.S b/Boot486/boot0.S
index 21608cb..9ff81fa 100644
--- a/Boot486/boot0.S
+++ b/Boot486/boot0.S
@@ -25,8 +25,9 @@
 # Stage 1
 # =========================================================================== #
 
-.code16
 _start:
+
+.code16
 stage1:
 # 1. Setup canonical %cs:%eip, segment registers %ds, %es, %fs, %gs, %ss and stack %sp
 	cli
@@ -41,10 +42,10 @@ stage1:
 
 	mov %dx, BootDiskAdr
 	call mapmem
+	sti
 
 # 2. Enable A20 gate
-	call enable_A20
-	sti
+	call enableA20
 
 # 3. Reset disk controller (%dl and %dh initialized by bios) and read Kernel into buffer
 	movl $(kernel_code_end - kernel_code_start), KernelSizeAdr
@@ -263,161 +264,39 @@ readsectors__success:
 	ret
 
 # =========================================================================== #
-# Check that A20 Gate is enabled
-#   output: set zero flag if disabled
-#   restore: %ds %es
+# Enable A20 Line
 # =========================================================================== #
 
 .code16
-check_A20:
-	push %ds
-	push %es
-#	push %ax
-#	push %di
-#	push %si
-
-	xor %ax, %ax
-	mov %ax, %es
-
-	not %ax
-	mov %ax, %ds
-
-	mov $0x0500, %di
-	mov $0x0510, %si
-
-	mov %es:0(%di), %al
-	push %ax
-
-	mov %ds:0(%si), %al
-	push %ax
-
-	movb $0x00, %es:0(%di)
-	movb $0xff, %ds:0(%si)
-
-	cmpb $0xff, %es:0(%di)
-
-	pop %ax
-	mov %es:0(%di), %al
-
-	pop %ax
-	mov %es:0(%di), %al
-
-	mov $0, %ax
-
-	je check_A20__exit
-
-	mov $1, %ax
-
-check_A20__exit:
-#	pop %si
-#	pop %di
-#	pop %ax
-	pop %es
-	pop %ds
-	or %al, %al
-	ret
-
-# =========================================================================== #
-# Enable A20 Gate
-# =========================================================================== #
-
-enable_A20:
-	/* First check */
-	call check_A20
-	jnz enable_A20__success
 
-	/* BIOS method */
-	mov $0x2401, %ax
-	int $0x15
-
-	call check_A20
-	jnz enable_A20__success
-
-	/* Keyboard method 1 */
-	mov $0xd0, %al
-	out %al, $0x64
-
-	call check_A20
-	jnz enable_A20__success
-
-	/* Keyboard method 2 */
-/*
-#	cli
-	
-	call enable_A20__wait1
-	mov $0xad, %al
-	out %al, $0x64
-
-	call enable_A20__wait1
-	mov $0xd0, %al
-	out %al, $0x64
-
-	enable_A20__wait2:
+enableA20:
+ 	cli
+	xor %cx, %cx
+enableA20_1:
+	inc %cx
+	jz enableA20_3
 	in $0x64, %al
-	test $1, %al
-	jz enable_A20__wait2
-
-	in $0x60, %al
-	push %eax
-
-	call enable_A20__wait1
+	test $0x2, %al
+	jnz enableA20_1
 	mov $0xd1, %al
 	out %al, $0x64
-
-	call enable_A20__wait1
-	pop %eax
-	or $2, %al
-	out %al, $0x64
-
-	call enable_A20__wait1
-	mov $0xae, %al
-	out %al, $0x64
-
-	call enable_A20__wait1
-#	sti
-
-#	call check_A20
-#	jnz enable_A20__success
-*/
-
-	/* Control port A method */
-	mov $1, %al
-	out %al, $0x92
-
-	call check_A20
-	jnz enable_A20__success
-
-	/* Fast method */
-	in $0xee, %al
-
-	call check_A20
-	jnz enable_A20__success
-
-	mov $msg_a20_failed, %si
-	call print
-#	cli
-#	hlt
-
-enable_A20__success:
-	ret
-
-/*
-enable_A20__wait1:
+enableA20_2:
 	in $0x64, %al
-	test $2, %al
-	jnz enable_A20__wait1
+	test $0x2, %al
+	jnz enableA20_2
+	mov $0xdf, %al
+	out %al, $0x60
+enableA20_3:
+	sti
 	ret
-*/
 
 # =========================================================================== #
 # =========================================================================== #
 # =========================================================================== #
 
 msg_mapmem_failed: .asciz "1"
-msg_a20_failed: .asciz "2"
 msg_chs_error: .asciz "3"
 msg_kernel_read_failed: .asciz "4"
-
 msg_protected_mode: .asciz ">5"
 
 current_sector:
diff --git a/Boot486/run.sh b/Boot486/run.sh
index a9c515f..4fc543e 100755
--- a/Boot486/run.sh
+++ b/Boot486/run.sh
@@ -1,4 +1,4 @@
 #!/bin/sh
 
 set -e
-qemu-system-i386 -s -m 1G -hda ../BlackBox.img
+qemu-system-i386 -s -m 26M -hda ../BlackBox.img
diff --git a/System/Mod486/Kernel.odc b/System/Mod486/Kernel.odc
index 0930a934abbc3460d332291c68553683af90ba9a..02f3ca45d366e1c26443e26e33ad4b59faf2385f 100644
GIT binary patch
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-- 
2.29.2