I can’t remember off the top of my head because it’s been a long while, but there’s some weird option inside the configurator that accounts for one of the things the early atom line doesn’t have that the default kernel expects out of x86 or x64 processors.
Of course, any binary program that was compiled with the expectation of that capacity would also have weird hangs and slowness, but (like I said, a while ago) that didn’t tend to cause a 1.3ghz atom to be slower than a 700mhz pentium m.