diff --git a/bios/rombios.c b/bios/rombios.c
index 9ea2dbc..ac918ad 100644
--- a/bios/rombios.c
+++ b/bios/rombios.c
@@ -4078,22 +4078,25 @@ BX_DEBUG_INT15("case default:\n");
 #endif
 
 
-void set_e820_range(ES, DI, start, end, type)
+void set_e820_range(ES, DI, start, end, extra_start, extra_end, type)
      Bit16u ES;
      Bit16u DI;
      Bit32u start;
      Bit32u end;
+     Bit8u extra_start;
+     Bit8u extra_end;
      Bit16u type;
 {
     write_word(ES, DI, start);
     write_word(ES, DI+2, start >> 16);
-    write_word(ES, DI+4, 0x00);
+    write_word(ES, DI+4, extra_start);
     write_word(ES, DI+6, 0x00);
 
     end -= start;
+    extra_end -= extra_start;
     write_word(ES, DI+8, end);
     write_word(ES, DI+10, end >> 16);
-    write_word(ES, DI+12, 0x0000);
+    write_word(ES, DI+12, extra_end);
     write_word(ES, DI+14, 0x0000);
 
     write_word(ES, DI+16, type);
@@ -4106,7 +4109,9 @@ int15_function32(regs, ES, DS, FLAGS)
   Bit16u ES, DS, FLAGS;
 {
   Bit32u  extended_memory_size=0; // 64bits long
+  Bit32u  extra_lowbits_memory_size=0;
   Bit16u  CX,DX;
+  Bit8u   extra_highbits_memory_size=0;
 
 BX_DEBUG_INT15("int15 AX=%04x\n",regs.u.r16.ax);
 
@@ -4179,11 +4184,18 @@ ASM_END
                     extended_memory_size *= 1024;
                 }
 
+                extra_lowbits_memory_size = inb_cmos(0x5c);
+                extra_lowbits_memory_size <<= 8;
+                extra_lowbits_memory_size |= inb_cmos(0x5b);
+                extra_lowbits_memory_size *= 64;
+                extra_lowbits_memory_size *= 1024;
+                extra_highbits_memory_size = inb_cmos(0x5d);
+
                 switch(regs.u.r16.bx)
                 {
                     case 0:
                         set_e820_range(ES, regs.u.r16.di,
-                                       0x0000000L, 0x0009fc00L, 1);
+                                       0x0000000L, 0x0009fc00L, 0, 0, 1);
                         regs.u.r32.ebx = 1;
                         regs.u.r32.eax = 0x534D4150;
                         regs.u.r32.ecx = 0x14;
@@ -4192,7 +4204,7 @@ ASM_END
                         break;
                     case 1:
                         set_e820_range(ES, regs.u.r16.di,
-                                       0x0009fc00L, 0x000a0000L, 2);
+                                       0x0009fc00L, 0x000a0000L, 0, 0, 2);
                         regs.u.r32.ebx = 2;
                         regs.u.r32.eax = 0x534D4150;
                         regs.u.r32.ecx = 0x14;
@@ -4201,7 +4213,7 @@ ASM_END
                         break;
                     case 2:
                         set_e820_range(ES, regs.u.r16.di,
-                                       0x000e8000L, 0x00100000L, 2);
+                                       0x000e8000L, 0x00100000L, 0, 0, 2);
                         regs.u.r32.ebx = 3;
                         regs.u.r32.eax = 0x534D4150;
                         regs.u.r32.ecx = 0x14;
@@ -4211,7 +4223,7 @@ ASM_END
                     case 3:
                         set_e820_range(ES, regs.u.r16.di,
                                        0x00100000L,
-                                       extended_memory_size - ACPI_DATA_SIZE, 1);
+                                       extended_memory_size - ACPI_DATA_SIZE ,0, 0, 1);
                         regs.u.r32.ebx = 4;
                         regs.u.r32.eax = 0x534D4150;
                         regs.u.r32.ecx = 0x14;
@@ -4221,7 +4233,7 @@ ASM_END
                     case 4:
                         set_e820_range(ES, regs.u.r16.di,
                                        extended_memory_size - ACPI_DATA_SIZE,
-                                       extended_memory_size, 3); // ACPI RAM
+                                       extended_memory_size ,0, 0, 3); // ACPI RAM
                         regs.u.r32.ebx = 5;
                         regs.u.r32.eax = 0x534D4150;
                         regs.u.r32.ecx = 0x14;
@@ -4231,7 +4243,20 @@ ASM_END
                     case 5:
                         /* 256KB BIOS area at the end of 4 GB */
                         set_e820_range(ES, regs.u.r16.di,
-                                       0xfffc0000L, 0x00000000L, 2);
+                                       0xfffc0000L, 0x00000000L ,0, 0, 2);
+                        if (extra_highbits_memory_size || extra_lowbits_memory_size)
+                            regs.u.r32.ebx = 6;
+                        else
+                            regs.u.r32.ebx = 0;
+                        regs.u.r32.eax = 0x534D4150;
+                        regs.u.r32.ecx = 0x14;
+                        CLEAR_CF();
+                        return;
+                    case 6:
+                        /* Maping of memory above 4 GB */
+                        set_e820_range(ES, regs.u.r16.di, 0x00000000L,
+                        extra_lowbits_memory_size, 1, extra_highbits_memory_size
+                                       + 1, 1);
                         regs.u.r32.ebx = 0;
                         regs.u.r32.eax = 0x534D4150;
                         regs.u.r32.ecx = 0x14;