At high altitudes, there's less atmosphere between you and outer space, so cosmic rays and other ionizing radiation don't face as much resistance through scattering.
I work at a research radar near Fort Collins, CO (alt: 1432m), and we have a Sun Blade 1000 with ECC, whose motherboard emits a curious "burp" sound each time it detects a memory error. It seems to do this about once every two hours. Also, the radar transmitters can sometimes emit small amounts of X rays. I've not noticed any increase in the "burps" when we've got the transmitter on.
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Except this was available more than a year ago, as 2x4, with each CPU having it's own memory bus too.
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Examples:
http://www.sun.com/servers/entry/v40z/
http://www.tyan.com/products/html/thundern4250qe.
At high altitudes, there's less atmosphere between you and outer space, so cosmic rays and other ionizing radiation don't face as much resistance through scattering.
I work at a research radar near Fort Collins, CO (alt: 1432m), and we have a Sun Blade 1000 with ECC, whose motherboard emits a curious "burp" sound each time it detects a memory error. It seems to do this about once every two hours. Also, the radar transmitters can sometimes emit small amounts of X rays. I've not noticed any increase in the "burps" when we've got the transmitter on.