Bad RAM

Most likely you've been there.  A system that has never seemed to be stable no matter how many times you wipe the drive, reload the OS change out drivers and hardware … you blame the CPU, you replace the motherboard, upgrade the BIOS, new hard drives.  You still seem to have problems off and on and you can't figure out why!

Have you done any memory testing?  I don't mean just the basic 'marching zeros' test that a startup BIOS runs, but real stress-testing to see what's under the hood?  Odds are in cases like this one or more of your sticks of DRAM are damaged and acting up only when certain strings of data or patterns of movement occur.  Memory is stored as voltage 'levels' in banks of registers, but the transfer of the data is all done via serial 'data lines' just like the data transfer to and from your hard drive. 

And just like those data lines noise always exists and is 'dampened' by a small electronic device called a 'capacitor' which is really just a small battery which resists change in voltage by changing current as necessary to try and stabilize the voltage.  When or if these little capacitors go bad the timing of your dram which is critical to the output being considered a 1 or a zero can no longer be counted on.  But then who has ever heard of a battery going bad, eh? 

Another problem is caused by 'mismatched' dram sticks – since most systems have only one data bus and will read and write to all the sticks at a preset speed it is important that you use DRAM from the same manufacturer with the same speed ratings if at all possible. At the very least be certain your least reliable (i.e. cheapest) DRAM module is at least rated faster then your system's recommended limits.

Don't go with the minimum specifications since over time remember those lil suckers will slow down, not to mention the manufacturer's tolerances may not be quite as good as you'd hoped and 'soft' failures (specifications not quite being met in all instances) may start to occur …

OK, I've probably scared you now but I didn't mean to!  DRAM is amazing stuff, and very resilient – bad ram is while not impossible by any means unlikely if proper static precautions have always been taken.  But if you get hangs and crashes, system reboots without any warning or odd video displays or audio hangs when system performance is peaking you probably need to pop the hood and give those old die-hard DRAM sticks of yours a good testing.  Odds are good that one or more is acting up …