[rollei_list] Re: CDs and reality of things

At 09:54 AM 4/16/2006 -0700, Peter wrote: 
Eric,

I am sorry to tell you that you are wrong! Regardless of your belief that you are an expert in this area, I can show you a few CDs that are more than 20 years old. As to your CDs that deteriorated, well, not sure what they were or how they were made, etc. But all I can say is I have a large CD collection many of which date to 1983 or so. So all I can say is you must be very rough on your CDs. There were some issues with early pressings but these were resolved. Today's commercial CDs will last many years.

OK. So now I am ready for you to tell me I am wrong because you know someone who knows an engineer, who test a CD for someone's company...yada yada yada.

Peter K

I agree with Peter with regard to commercial CDs, just based on their construction. For some reason (probably because I'm a saver, something might just come in handy some time you know) I have many AOL CD's from long ago that still read perfectly. (No, I don't use AOL, I just get CD's from them regularly) It may be that in the early days the cover plastic might have had a different coefficient of expansion, or a different chemical makeup, than the base section which holds the stamped image, but if that problem ever existed, it's surely not with us these days.

I have never had a problem with a self-burned CD-R EXCEPT in a couple of cases. I got some cheap ones from Fry's and they didn't even complete burning. I also got some cheap CD-R blanks which indeed failed right away, just after a day or so. Now I buy only brand names and don't have any problem.

In other cases, I found that burning CDs much slower than their max rated burn speed created defective CD's, no idea why, however. My thought was that slower burning would provide more energy to the surface, making a better burn, but that's just a guess.

With respect to R/W CDs of any flavor, one would reason that there is a wear limit to the number of times the phase change can be done, just as there was with early digital media chips. I remember that the HP 95-200LX handhelds had (still have) a "wear" program, which scans the media, checks for places with weak signals, and switches them out and moves the data to fresh spots. I still use my 200LX about once a day and have done so for several years, however the wear program has never reported a bad spot.*

I also keep an "archive" re-writable CD in one of my drives and have been backing up to it several times daily for at least 5 years. So far no errors, although there should have been some by now.

Finally, I have an adapter and use a smart media and compact flash card in it and also back up my accounting data on them as well as the CD every day. No errors yet, but that may still happen.

*Speaking of "bad spots", my current digital cameras also have a similar program, which removes bad sensor elements from service and somehow manages to create something equivalent to a good spot at the same location. So far, running this program has never reported a bad spot.


Don Williams
La Jolla, CA

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