A little rant about CD drives

It blows my mind how many corrupted ISO dumps there are floating around out there. I try to check for at least basic functionality of anything on Winworld, but you might never know if the ExtraCrap.mpg file hidden seven directories deep in some BS filled extras folder has a single bit flipped somewhere that doesn't even cause it to fail.

While one might argue about the lack of any kind of CRC or checkum protection in the ISO format (once it is in a 7z file that is no longer an issue), that does not do any good when most of the issues I have seen seem to be due to damaged CD-roms or faulty CD drives.

First of all, when dumping a CD or DVD ROM, it is critical to keep an eye out for any errors reported by your dumping tool. We recommend ImgBurn, and it does a fairly good job of letting you know when there is a serious error. If there are any warnings or if the drive seems unhappy, then ImgBurn has the ability VERIFY the newly dumped ISO image against the CD.

If there are ANY read errors, try dumping again. Very often cleaning a CD with isopropyl alcohol and then applying a layer of furniture polish (such as Endust or Pledge) using a soft cloth will take care of small scratches. If there still problems, ALWAYS make a note of it and include it with the file, even if you "test" the content of the ISO somehow and it seems to work for you.

Of course, that does not do much for faulty CD drives. The bizarre thing is that the physical CD-ROM format is built upon layer upon layer of error correction and error detection. Yet somehow some CD drives will just fudge bad reads and happily send the resulting shit along its way as if it were good data. This is what happens when you try to build a CD drive with cheap foreign labor for only $5 each. And the typical way CD drives fail over time is start getting more and more intermittent read errors over time - which, of course, gets passed on as good data. Then you also get things like faulty buffer RAM that only shows up under certain circumstances.

Is there NO error checking on the IDE or SATA bus? Over the years I have had perfectly good drives return garbage due to crap IDE drives hooked on the same cable, or even just faulty cables. (Seriously, I recall recovering data from an IDE hard drive that "crashed" after writing some data - and all of the data it wrote had one bit stuck in every single byte. The problem was a flaky cable)

The one I have not figured out yet is how some CD burners somehow alter data that is sent to the drive. I have seen this multiple times, and it is repeatable. The weird thing is it is usually with Jpeg images. Literally some specific pattern of data triggers something in the drive. (Perhaps trying to treat it as a "photo CD" instead of data CD?) At least ImageBurn catches that during its write verify process and give me a big fat error. And a brand new coaster.

Of course, data corruption is not unique to CD drives. Any time you dump a floppy with Winimage and hit "ignore", dump a SCP/Kryoflux image and don't verify with HxC only to find out later a head got gunked, flash drives get damaged and loose bits, hard drives can crash and corrupt sectors, your fancy encryption to your cloudy server can mess things up if you have bad RAM. I've even come across a very specific data pattern that will randomly flip a bit when passed across certain old VIA IDE chipsets (tested on multiple machines).

Then the real kick in the nuts is when the file is posted somewhere, downloaded hundreds of times, and nobody says jack shit.

So the moral is check, check, re-check, compare to multiple sources, and don't assume everything always works perfectly.


  • yup, re everything said. Do you have a setting or trick that prevents Imageburn from "overdumping"? I just tried it out on Win 98SE OEM and it has the extra zero bytes on the end - as most softs tend to. On the other hand, (at least when dealing with Microsoft products) I can use WinImage and get a SHA1 matching image every time. Error checking and alerts of course is another issue.
  • Arag. I had tried very hard to forget about that. :P

    My incredibly vague recollection is that one of the major popular CD burning programs out there a long time ago (late 1990s/early 00s?) had a very serious off-by-one error. I recall having to manually add zero padding to ISO files way back then just to make it happy. I forget if that was before or after it made a coaster. I guess adding zero padding at the end just became standard and ImgBurn takes care of that for you.

    At any rate, ImgBurn has piles of options, there might be something in there about that. I normally recommend this specific version: https://winworldpc.com/product/imgburn/2x because it is well tested on 95 and some later versions had issues making bootable CDs. Although I think very often that extra zero padding gets written to the CD, so it becomes part of the CD.
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