Strange corruption of CD-ROM I/O

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2 total messages Started by Ben Peddell Sat, 02 Aug 2003 11:18

#132

Author: Ben Peddell
Date: Sat, 02 Aug 2003 11:18

22 lines
2573 bytes

I have a 3-year old 36x CD-ROM drive, and it seems to be failing.
It has trouble reading CDRs that it could read a month or so ago (and 
that other computers can still read).

Last night, it was fairly cold (about 10C), and it had strange 
corruption of disks that I knew were perfectly OK. In Cooked mode, it 
kept getting read errors. In RAW mode, it got no errors, but it seemed 
to be reading 156 bytes too soon, and xor-ing with a certain pattern.
This made sector 0 of the BIN file to start with the 156 bytes from the 
end of sector -1, and thus Daemon-Tools Stealth-DVD complained that 
there were no sync bytes.
Audio was read fine though (from the same CD).

I was able to recover the data from the CD-ROM image (by seeking 156 
bytes and XORing each sector with the pattern based on the first (empty) 
sector.

The XOR pattern was constant along the entire Data portion of the image. 
It was even repeated in another image that was partly read.

I'm wondering if anyone can speculate, or has any thoughts on this.
If someone wants, I could make the XOR pattern available for others.

Re: Strange corruption of CD-ROM I/O

#133

Author: Ben Peddell
Date: Sun, 03 Aug 2003 15:12

55 lines
3664 bytes

Phax0r wrote:

 >Ben Peddell wrote:
 >
 >
 >
 >>I have a 3-year old 36x CD-ROM drive, and it seems to be failing.
 >>It has trouble reading CDRs that it could read a month or so ago (and
 >>that other computers can still read).
 >>
 >>Last night, it was fairly cold (about 10C), and it had strange
 >>corruption of disks that I knew were perfectly OK. In Cooked mode, it
 >>kept getting read errors. In RAW mode, it got no errors, but it seemed
 >>to be reading 156 bytes too soon, and xor-ing with a certain pattern.
 >>This made sector 0 of the BIN file to start with the 156 bytes from the
 >>end of sector -1, and thus Daemon-Tools Stealth-DVD complained that
 >>there were no sync bytes.
 >>Audio was read fine though (from the same CD).
 >>
 >>I was able to recover the data from the CD-ROM image (by seeking 156
 >>bytes and XORing each sector with the pattern based on the first (empty)
 >>sector.
 >>
 >>The XOR pattern was constant along the entire Data portion of the image.
 >>It was even repeated in another image that was partly read.
 >>
 >>I'm wondering if anyone can speculate, or has any thoughts on this.
 >>If someone wants, I could make the XOR pattern available for others.
 >>
 >>
 >
 >Yeah, right, 'strange' that metal shrinks and plastics shrink (and, 
crack!)
 >and the alignment is off, when it drops from what? 24C? to 10C? 
Temperature
 >fluctiuations of only 8 to 10 degrees C I can expect to be tolerated, but,
 >NOT anything above about 10C difference!
 >
 >
 >
 >
 >

The CDs are still fine. The CD-ROM drive is able to read them fine now
that it's not nearly so cold (about 20C), with a daytime temperature of
maybe 25-30C. I'm in North Queensland, Australia, so yes it could have
been the extreme temperature changes playing havoc with the drive's
electronics.
It just seemed strange that drive's controller was reading too soon and
corrupting the data with a fixed pattern on certain CDs.
The drive continues to get worse with reading CDRs though. I'll be
replacing it with a Combo drive soon.

Thankyou for your insight.
Ben.

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