T1E1
13 April 2011 | Bug Reports | CRC error checking in SectorEdit?
I\'m not 100% sure if this is a problem with the program, but here\'s what I have found. Forgive the length, but I want to make sure enough information was given so you know what I\'m doing.
Environment:
- Windows XP Pro
- legacy 1.2MB 5.25\" floppy diskette drive connected through motherboard floppy header
- ASUS P4P800 motherboard
- diskettes last written to about 20 years ago
- MS-DOS 3.3 FAT12 format, but while FATs and directory structures exist, the data on disk is not not organized into a file that appears in the disk directory or in the FAT tables. This was intentional by the manufacturer and is not disk damage.
I just found Sector Edit a few days ago and it\'s perfect for what I need to explore diskettes at the sector level. Beyond exploration, the other thing that I need to do is to create images of these diskettes so that as they further degrade over time, I can re-create them in the future. I know you created DiskImage for that, but I didn\'t find that program until I had started using SectorEdit for the same function.
Method:
- Insert diskette in drive.
- Open SectorEdit
- Specify drive \"Logical A:\"
- Select File/Export Sector(s)
- Specify a filename.
- Enter 2400 as the number of sectors, which is what is specified in Sector 0 as the number of sectors (1200K)
- SectorEdit saves file.
Here\'s the problem:
The first diskettes I did this on were three copies that were supposed to be factory identical. I created images of each. Out of curiosity, I used a file comparison tool on the .bin files to check and see if they were truly identical. Diskettes 2 and 3 were identical, but 1 was different. I then figured out what sector and offset the differences were and looked at copy 1, direct off of the diskette. The data that came up in SectorEdit was what had appeared in the export files from copies 2 and 3, not what had been read off of copy 1. I re-exported copy 1 to a separate .bin file and this time it compared correctly to 2 and 3.
So... I know the diskettes are aging and I\'ve had problems reading (on the same hardware, through Windows copy/paste) other diskettes of similar age that have traditional DOS file structure. I wouldn\'t be surprised that there are CRC errors on some sectors. However, when using SectorEdit, I\'ve never encountered any read errors, but I have had this problem on two different occasions so far after reading six diskettes twice each. I want to use SectorEdit and/or DiskImage to create the archive (of the many floppy disks that I have), but I\'m not sure if I can rely on the data being saved...
So the root question becomes whether SectorEdit and/or DiskImage do the same CRC checking that a Windows Copy/Paste does? What reason could there be for SectorEdit to give two different .bin files with different contents when reading the same diskette, and without getting a read error message?
Any comments would be appreciated. |
