The bug would cause the system to lock up and is a difficult issue to determine without having Intel actually look at the chip. Chips that passed the test, and all subsequent chips which were bug-free, were marked with a double-sigma symbol.
386DX chips that are not marked with either of these symbols may have not been tested by Intel and may be defective.
PENTIUM - One of the most famous and most known bugs is the Pentium FPU flaw / bug discovered by a a mathematician in October 1994. This bug involved the Pentium incorrectly performing floating-point calculations with certain number combinations, with errors anywhere from the third digit on up.
This issue does not occur on 120MHz and above Pentium computers, however is known to occur on Intel Pentiums 100MHz and below.
Ways of testing your Pentium CPU to determine if it has the Pentium flaw.