Is the old pentium safe? Or the and fx CPUs? I love how far and and Intel have come, and how you can get a massive arm CPU, but these modern hardware security

Is the old pentium safe? Or the and fx CPUs? I love how far and and Intel have come, and how you can get a massive arm CPU, but these modern hardware security issues seem to be a more frequent issue(is this true?) And to stop them one takes a decent performance penalty..... Which is way less than ideal.