Ultimate: The Ultimate Image Browser: Modify new MBR image

• Some systems like to have a 32-bit disk signature at offset 0x1B8.
  • Click on the '<<' button next to the Signature field to give it a random signature value.
• These same systems like to have the 16-bit value at offset 0x1BC zero.
  • If this value is not zero, you may enter a value of 0x0000 here.
• The values in the "CHS Calculation Values" are used when calculating the CHS values in each entry.
  • See below where these values are used.
• The large box underneath is simply to show the values in this sector
• The Update MBR Code button allows you to update the MBR code.
  • Clicking on the button will ask for a file name.
  • Choose a 512-byte file that contains valid MBR code.
  • This will not overwrite any partition entry, the signature, or the zero field, unless the associated checkbox(es) are checked.
  • You do not have to click on the APPLY button to update the MBR code.
  • The large dump box should now be updated to show the new contents.
• The Update MBR Sig button simply ensures that the value at 0x1FE is 0xAA55.
  • Clicking on the button will write this value to this address.
• The Prepend MBR button inserts sectors before the image.
  • On a rare occasion (I needed to once), you might wish to prepend empty sectors to the image file.
  • This function will ask how many sectors to prepend and then prepend sectors to the image file.
• The Overwrite Partition Table checkbox will allow the new MBR code (using the Update MBR Code button) to overwrite the existing Table.
• The Overwrite Disk Identification checkbox will allow the new MBR code (using the Update MBR Code button) to overwrite the existing Signature and Zero fields.
• The Is Legacy GPT Boot checkbox will allow the new MBR code (using the Update MBR Code button) to overwrite the existing GPT Header.
  • If the utility found a GPT at LBA 1, and the MBR code you are writing to LBA 0 (using the Update MBR Code button) is more than one sector, this will allow the existing GPT Header to be over written by the new code.
  • If this checkbox is cleared, only the first sector will be overwritten.

Partition Entries

• Boot ID:
  • The Boot ID field should be 0x00 or 0x80 but allows you to put any 8-bit value.
• Start CHS fields:
  • These are the starting CHS fields for the associated partition.
  • You may put any 8-bit value in either field.
  • If you click on the button to the right, the utility will place the correct values from the Starting LBA field below.
• Sys ID:
  • The Sys ID field is the Partition Type field.
  • You may put any 8-bit value in this field.
  • You may click on the Sys ID: button to choose a type.
  • The description box just to the left should update to a type as you enter a value.
  • Note that Ultimate will not see any partitions until the Sys ID field for that partition is non-zero.
• End CHS fields:
  • These are the ending CHS fields for the associated partition.
  • You may put any 8-bit value in either field.
  • If you click on the button to the right, the utility will place the correct values from the Starting LBA and Sector Count fields below.
• Starting LBA
  • This is the 32-bit LBA value of the first sector in the partition.
  • Please note that if you modify this value, the utility will not "move" the partition for you. It only modifies this value.
• Sector Count
  • This is the 32-bit sector count of sectors in the partition.

Applying your changes

• Any changes to any partition entry must have that entry's Apply button used or the change will not be written to the image.
  • Note that if an entry is modified, there will be a star '*' next to the entry name on the tab control.
  • Note that clicking on the Apply button only updates the entry, it doesn't actually write it to disk. See next item entry.
• Note that most items are not actually written to disk until you click on the Apply button in the lower right corner.
  • The Update MBR Code does not need the Apply clicked.
  • A few other items do not need the Apply clicked.
  • However, if you are not sure, simply click the Apply button anyway, to ensure that the sector is written to disk.

Complete

• updated the MBR code using the Update MBR Code button.
• Give it a signature using the Signature button.
• Marked the first partition as bootable (0x80 in the Boot ID field).
• Updated the Starting and Ending CHS values using the two respected buttons.
• Chose the FAT 16 (less than 32 Meg in size) partition type id.
• Clicked the Partition Entry's Apply button.
• Clicked the main tab's Apply button.
• I then reloaded the image using the File->Reload menu option.

FAT 16 partition format

• Click on the Format button and choose FAT 16.
• Now you will be asked for a file.
  • This is the file to use for the boot code for this format.
  • It can be more than one sector in size.
  • This file's contents will be placed at the first sector of this partition.
  • If you wish to skip this step, simply click the Cancel button.
• A dialog will appear asking for some information about the format.

• This will populate with some default values for the format you have chosen.
• You may choose other values.
• If there were no errors, the utility should indicate that the format has been completed.
• The dump window will now be updated to the first sector of the partition.
• Use the File->Reload menu option to reload the image.