BIOS - Revision history

InvoxiPlayGames: /* Components */ 2BL exists there on all BIOSes that contain a FBL

2024-01-10T19:14:08Z

‎Components: 2BL exists there on all BIOSes that contain a FBL

JayFoxRox: Add skeptical note about 4132 / 4134

2020-05-26T14:31:12Z

Add skeptical note about 4132 / 4134

Furon: There are actually two initialization tables and the first is for the NV2A, not the MCPX.

2017-10-29T01:42:28Z

There are actually two initialization tables and the first is for the NV2A, not the MCPX.

Furon: /* Components */

2017-10-27T23:45:21Z

‎Components

Furon: /* Unknown */

2017-10-27T23:45:00Z

‎Unknown

JayFoxRox at 13:47, 25 August 2017

2017-08-25T13:47:47Z

KaosEngineer: 8 nibbles instead of 9 for 0x0000007F Unknown region address range

2017-07-05T08:04:59Z

8 nibbles instead of 9 for 0x0000007F Unknown region address range

KaosEngineer: Hex goes to F not 9 just a little correction 0x00 - 0x7F instead of 0x79 for unknown address range

2017-07-05T08:01:57Z

Hex goes to F not 9 just a little correction 0x00 - 0x7F instead of 0x79 for unknown address range

JayFoxRox at 23:55, 18 June 2017

2017-06-18T23:55:28Z

JayFoxRox: /* Components */

2017-06-18T22:30:43Z

‎Components

@@ Line 41: / Line 41: @@
 |-
 ! 2BL <br> ''Always 0x6000 bytes''
-| 0x39E00 || 0x39E00 || 0x39E00 ||         ||         ||         ||         ||
+| 0x39E00 || 0x39E00 || 0x39E00 || 0x39E00 || 0x39E00 || 0x39E00 || 0x39E00 || 0x39E00
 |-
 ! FBL <br> ''Always 0x2880 bytes''

@@ Line 20: / Line 20: @@
 {| class="wikitable"
+!
-!   3944  !!   4034  !!   4134  !!   4817  !!   5101  !!   5530  !!   5713  !!   5838
+!   3944  !!   4034  !!   4134{{FIXME|reason=Some sources claim there is 4132; however, neither 4134 or 4132 are listed in redump. So this might not be a real MS bios}} !!   4817  !!   5101  !!   5530  !!   5713  !!   5838
 |-
 ! NV2A Initialization Table

@@ Line 22: / Line 22: @@
 !   3944  !!   4034  !!   4134  !!   4817  !!   5101  !!   5530  !!   5713  !!   5838
 |-
-! MCPX Initialization Table
+! NV2A Initialization Table
 | 0x00000 || 0x00000 || 0x00000 || 0x00000 || 0x00000 || 0x00000 || 0x00000 || 0x00000
 |-
 ! X-Codes
@@ Line 49: / Line 52: @@
 For information how these sections are used, see [[Boot Process]].
-=== MCPX Initialization Table ===
+=== NV2A Initialization Table ===
-From 0x00000000 - 0x0000007F
+The first DWORD of the NV2A initialization table is the magic number 0x2B16D065 (called the "boot header"). The purpose of the remaining values in the table is unknown{{FIXME}}.
-The first DWORD is a pointer to a table of values that the MCPX core uses to initialize itself, but with the least-significant bit always set to 1. The second DWORD is the unmodified table pointer. On all Xbox BIOS, the MCPX initialization table is always at file offset 8, virtual address 0xFF000008.
+=== MCPX Initialization Table ===
-The first DWORD of the MCPX initialization table is the magic number 0x2B16D065 (called the "boot header"). The purpose of the remaining values in the table is unknown{{FIXME}}.
+This is a table of values used to initialize the MCPX southbridge. It ''must'' be placed at offset 0x70 in the ROM image.
 === xcodes ===

@@ Line 22: / Line 22: @@
 !   3944  !!   4034  !!   4134  !!   4817  !!   5101  !!   5530  !!   5713  !!   5838
 |-
-! Unknown
+! MCPX Initialization Table
 | 0x00000 || 0x00000 || 0x00000 || 0x00000 || 0x00000 || 0x00000 || 0x00000 || 0x00000
 |-

@@ Line 49: / Line 49: @@
 For information how these sections are used, see [[Boot Process]].
-=== Unknown ===
+=== MCPX Initialization Table ===
 From 0x00000000 - 0x0000007F
-Not sure what this does. Some people think it might be involved with initialising the [[MCPX]]{{citation needed}}. The Reset Vector on the Pentium 3 would mean that this wasn't called before the MCPX ROM{{citation needed}}.
+The first DWORD is a pointer to a table of values that the MCPX core uses to initialize itself, but with the least-significant bit always set to 1. The second DWORD is the unmodified table pointer. On all Xbox BIOS, the MCPX initialization table is always at file offset 8, virtual address 0xFF000008.
 === xcodes ===

@@ Line 1: / Line 1: @@
-The '''BIOS''' (an acronym for '''Basic Input/Output System''' and also known as the '''BIOS ROM''' or '''Xbox ROM''') is a firmware image that is mapped to the top 16MiB of the CPU's physical address space (0xFF000000-0xFFFFFFFF). Like the standard [https://en.wikipedia.org/wiki/BIOS PC BIOS], it is responsible for initializing the Xbox hardware and booting the system. Unlike the PC BIOS, however, the Xbox BIOS image also contains the kernel in a compressed and encrypted form.
+The '''BIOS''' (an acronym for '''Basic Input/Output System''' and also known as the '''BIOS ROM''' or '''Xbox ROM''') is a firmware image that is mapped to the top 16MiB of the CPU's physical address space (0xFF000000 - 0xFFFFFFFF). Like the standard [https://en.wikipedia.org/wiki/BIOS PC BIOS], it is responsible for initializing the Xbox hardware and booting the system. Unlike the PC BIOS, however, the Xbox BIOS image also contains the kernel in a compressed and encrypted form.
-On a standard Xbox, the BIOS image is stored in the [[Flash]]. The BIOS image is actually 256KiB, duplicated 4 times to fill the 1MiB ROM chip. You can verify this by running:
+On a standard Xbox, the BIOS image is stored in the [[Flash ROM]]. The BIOS image is actually 256 kiB, duplicated 4 times to fill the 1 MiB ROM chip. You can verify this by running:
 <pre>
@@ Line 12: / Line 12: @@
 </pre>
-You'll notice it is the same file repeated 4 times. That explains how some BIOS chips are 1MB and some are 256KiB. The next thing is that the BIOS is repeated from 0xFF000000 until it fills the rest of memory. In other words, that 256KiB of data is repeated 64 times.
+You'll notice it is the same file repeated 4 times. That explains how some BIOS chips are 1 MiB and some are 256 kiB. The next thing is that the BIOS is repeated from 0xFF000000 until it fills the rest of memory. In other words, that 256 kiB of data is repeated 64 times.
 == Components ==

@@ Line 51: / Line 51: @@
 === Unknown ===
-From 0x00000000 - 0x000000079
+From 0x00000000 - 0x00000007F
 Not sure what this does. Some people think it might be involved with initialising the [[MCPX]]{{citation needed}}. The Reset Vector on the Pentium 3 would mean that this wasn't called before the MCPX ROM{{citation needed}}.

@@ Line 31: / Line 31: @@
 | 0x00CFA || 0x00CFA || 0x00CFA || 0x00DB9 || 0x00E49 || 0x00E59 || 0x00E59 || 0x00DCC
 |-
 ! Kernel
-|         ||         ||         ||         ||         ||         ||         ||
+| 0x0619C ||         ||         ||         ||         ||         ||         ||
 |-
 ! Kernel Data Segment
-|         ||         ||         ||         ||         ||         ||         ||
+| 0x3944C ||         ||         ||         ||         ||         ||         ||
 |-
-! 2BL
+! 2BL <br> ''Always 0x6000 bytes''
 | 0x39E00 || 0x39E00 || 0x39E00 ||         ||         ||         ||         ||
 |-
-! FBL (Start & Entry point)
+! FBL <br> ''Always 0x2880 bytes''
 |         ||         ||         || 0x3D400 || 0x3D400 || 0x3D400 || 0x3D400 || 0x3D400
 |-
 ! Decoy Boot Loader

@@ Line 39: / Line 39: @@
 ! 2BL
 | 0x39E00 || 0x39E00 || 0x39E00 ||         ||         ||         ||         ||
 |-
 ! Decoy Boot Loader
@@ Line 64: / Line 70: @@
 This leads me to believe that the first three BIOS versions that I have are compatible with the 1.0 MCPX, and the rest are compatible with the 1.1 MCPX.
-Next, some people believed that there was another unknown section between the xcodes and the copyright string. As far as I can tell, that section was to allow the xcode instruction set to expand, as the 5838 instructions are considerably larger than those in the 3944 BIOS.
+Next, some people believed that there was another unknown section between the xcodes and the copyright string. As far as I can tell, that section was to allow the xcode instruction set to expand, as the 5838 BIOS has considerably more xcodes than the 3944 BIOS.
 === Copyright String ===