We do everything we can to stop failing subsystems from ever entering our customers hands. We beat on our systems, usually with loads far in excess of what our customers will do. No, not using memtest. We run real codes. And we catch lots of problems.
What surprises me, really gets to me, is that some motherboard makers (who shall remain nameless) ship product to their customers (us) for integration into our products, or as subsystems into products we buy from others, and this product does not work. Oh, well it might work in a narrow regime of less than 4 GB ram, and one processor, and no PCI cards. But try to configure and push this unit to where our customers will? Fuhgeddaboutit.
http://www.linuxlinks.com/portal/news/article.php?story=20061101132901718