Bitflip error

Bernhard on 2007-06-24T20:22:00

On Friday a colleague @work asked me about an error in a webapplication. There was a Perl syntax error in Sys::Hostname. As I saw no reason that anybody should mess with with Sys::Hostname, I checked the time Hostname.pm was last changed. Confusingly the last change was in 2004, apparently this was the time the server was set up. A diff with another Perl 5.8.0 installation showed a single bit change. The first space, 0x20, of Hostname.pm line 104 has turned into into a '(', 0x28. The only explanation I can imagine is that a bit has flipped in file cache.

Strange.


Yeah

Aristotle on 2007-06-25T05:52:39

It does happen. Funny that it was a Perl module involved in both cases.

Re:Yeah

Bernhard on 2007-06-25T07:39:18

Thanks for that link. One bit per Gigabyte and month sounds like a lot to me.

My physics diploma thesis was about radiation hardness of the pn-CCD detector of the XMM X-Ray observatory, http://wave.xray.mpe.mpg.de/xmm. When testing the CCDs we could see protons and alpha particles showing up as black streaks. Black meaning out of the dynamioc range of the charge measurement electronics. This was the sign that the setup was working.

I guess that the CCDs of digital pocket cameras have an error correction for that.