A more serious floating point bug showed up in the original version of Intel's Pentium processor. The flaw, first exposed in 1994 by InformationWeek.com's own Alex Wolfe, occurred in the chip's Floating Point Unit, and produced math errors in various types of calculations. Intel insisted the bug would affect only a tiny minority of users under very limited circumstances. But tests showed the errors could be reproduced relatively frequently when Pentium computers were used for a number of calculations commonly used in science. Intel ultimately agreed to replace the affected chips upon request, taking a $475 million charge to cover the losses.
Further reading: IT Hall Of Shame, Part 1