What gets put in an MBR other than the Partition Table?

When ADD modifies the partitions on a drive, does anything in the MBR, other than the Partition Table, get modified?

In particular is anything modified in the boot sector, i.e., the first 446 bytes of the MBR?

 

Howard:

No, it should not modify anything in the first sector other than some of the bytes in the 64-byte partition table.

You could copy the first sector of your disk to a file (file #1) then modify the partitions with DD, then again copy the first sector to a file (file #2). Compare file #1 with file #2 to find out which bytes are modified.

If I had a few extra minutes I'd do this in a VM to demonstrate. Unfortunately, work beckons...

 

I'll do that.

A few daze ago, I used Recovery Console to clean up the MBR on each of 4 drives. Hopefully, there's no Partition Magic crap left behind.

 

What do you use to copy the first sector?

I do so by booting to Ubuntu and copying there.
Is there a way to do this in Windows?

 

You can use Disk Director to do this. Use the Disk Editor to view the first sector. Highlight all of the bytes in the first sector and save it to a file on your disk.

The disk editor is also handy for comparing two sectors. If you copy the saved file to a blank sector on your disk and then copy the second file on top of the first, the differences will be shown in color. The blank sectors between 2 and 62 are handy for this purpose. You can write zeros back to them when finished.

 

You can use the Disk Editor in DD to save Sector 0 to a file. Once saved, you can then read the file back in. Changes will be a different color (I think green) so you can easily see what's been changed. Don't commit the changes (save the sector) if you want to leave it like it is.

 

Howard:

Here is an example from Virtual XP. The following two pictures are the virtual disk layout before and after adding a partition:




This is the first sector on the disk before adding the new partition:



And this is the first sector after adding the new partition. The changed bytes are in green:



As you can see, only the third slot of the partition table was modified. None of the other bytes changed.

 

I'm just about convinced that the problem causing slower performance of Ubuntu 9.04 vs Ubuntu 7.04 is not the swap partion's location.

I believe that it is the generic video driver used for the Radeon card.

Using System Monitor in Ubuntu shows that the swap partition is not even being used, and there is plenty of unused memory, but screen updatunfg is veeeery slow.

I'll go to Radeon's web site and see what drivers they have.