DOS and WFW 3.11 -- Fresh install (unopened retail boxes)

[Steven W]

Are there any known issues with applying these fixes? Can anyone think of any potential issues?

Edited July 28, 2013 by Steven W

[rloew]

If you apply these fixes, you stand a greater chance of having two Disks with the same checksum, especially if you do raw copies of the Disks.

The same thing applies to Hard Drives if the second fix is applied. Duplicate Volumes will be melded into one and can crash if they are removed.

Duplicate Hard Disk MBR checksums can lead to the Disks being swapped, resulting in possible corruption.

This can also occur using the other alternatives described previously or if a Disk is Write Protected.

It is important when copying Disks or Partitions that you ensure they have unique Checksums. Some tools do this automatically, others don't.

I have added checks and fixes to my Copying, Partitioning and Formatting tools for this.

[jaclaz]

Another Patch stops Windows from doing the same to non-standard MBRs.

Can you provide any detail/reference/whatever about this behaviour?

Are you talking of the "mistery bytes"?

http://thestarman.pcministry.com/asm/mbr/mystery.htm

From the above this can happen only if all six bytes at 0DAh-0DBh are 00's on the "non-standard MBR".

jaclaz

[rloew]

Another Patch stops Windows from doing the same to non-standard MBRs.

Can you provide any detail/reference/whatever about this behaviour?

Are you talking of the "mistery bytes"?

http://thestarman.pcministry.com/asm/mbr/mystery.htm

From the above this can happen only if all six bytes at 0DAh-0DBh are 00's on the "non-standard MBR".

jaclaz

Yes. But they are no mystery to me.

I already had an Amiga SCSI Hard Drive disabled by this, simply by trying to read the Disk with an Adaptec Card.

It has far less data in Sector 0, so these addresses were unused. The problem is that the entire Sector is Checksummed.

[jaclaz]

Yes. But they are no mystery to me.

Sure they are not (at the very least since 2004).

I already had an Amiga SCSI Hard Drive disabled by this, simply by trying to read the Disk with an Adaptec Card.

It has far less data in Sector 0, so these addresses were unused. The problem is that the entire Sector is Checksummed.

A very good real life example of what can happen , though, still - of course IMHO - not "an everyday occurrence" to connect a SCSI Amiga disk to a Win9x .

jaclaz

[rloew]

Never said it was an everyday occurrence.

[jaclaz]

Never said it was an everyday occurrence.

Never said you said it.

I said how it probably was not one of them.

I will cite the already given link:

http://thestarman.pcministry.com/asm/mbr/mystery.htm

We purposely displayed a string of ZERO-bytes in the code shown above, because that's how these bytes are hard coded in all the FDISK.EXE utilities for Win 95B, 98, 98SE and Me. As a matter of fact, if you use the FDISK from one of these OSs with the /MBR switch on any drive, all of its "mystery bytes" will be overwritten with zeros! The FDISK program never writes anything but zeros to these locations. So, what does change these bytes? The Windows OS itself changes the last four of these six bytes whenever they are all zeros!

....

At first, you might think that an OS which overwrites code in any MBR sector might lead to some serious problems in Boot Manager software. But a bit of reflection will soon show that it'd be highly unlikely that any MBR code (or data for that matter) would ever place a string of six zero bytes at this particular location.

Possible? Yes .

Good example from the good MS guys of the worst possible approach (including arrogance, stupidity and a number of other attributes I am too polite to express) to "stamp" something within an OS or software? Yes.

Probable/likely to occur and cause havoc? No.

The only issue is when you make a "dd-like" clone and BOTH original and clone are connected/mounted, and, to cite again:

So, an intelligent technician that needs to copy the same Win9x/Me drive contents to many physical drives, would be sure to start with an image copy that has all zeros in these six bytes!

To sum up, IMHO something that everyone dealing with these activities should know about but not something that one wouldn't sleep about.

Ooops , I gotta go , I am late for the daily check on my meteorite shielding device ....

jaclaz