"Unadulterated original x86" doesn't really exist, and hasn't mattered for decades at least. Do you mean the 8086's instruction set? Many of those instructions

"Unadulterated original x86" doesn't really exist, and hasn't mattered for decades at least. Do you mean the 8086's instruction set? Many of those instructions are now implemented in microcode; sure, you can use them, but they're going to be dog slow. Turns out, nobody uses them. Do you mean the i586 instruction set? Your system calls are going to be slow, since you have to trigger an interrupt. Do you just mean 32-bit x86? That covers a large set of incompatible extensions among different vendors, and is of rapidly decreasing relevancy. Do you just mean scaler instructions? That's really just hamstringing yourself: a lot of performance-sensitive applications involve manipulating vectors, and SIMD is a fairly easy and effective win.