All three are pretty much the same, just loops of varies math functions. Chances are once they get loaded into the cpuís cache thatís mostly what gets tested not external memory, and even then they concentrate mostly on the FPU.
Since memtest locked up, the first thing I thought was FSB or memory. One thing memtest does is that it re-locates itself in memory so it can also test locations where it was running from and also turns the cache on and off. Meaning sometimes its really running from external memory.