Another source of error that you could introduce is from the clock signal. The reference oscillator on the motherboard could be defective or damaged and produce incorrect timings. Usually the clock signal is generated by a piezoelectric crystal, and then multiplied to even higher frequencies using a phase locked loop. If the phase locked loop is damaged or incorrectly designed, the resulting clock signals could be incompatible with the RAM even if you configure the correct timings in the BIOS settings.