Chrome 89 and above will require x86 processors with SSE3 support,” Google wrote. “Chrome will not install and run on x86 processors that do not support SSE3.”
SSE3, which stands for “Streaming SIMD Extensions 3,” was one of several — the third, in fact — add-ons to the x86 instruction set used by Intel (and later, AMD) processors. Intel introduced SSE3 to its Pentium 4 processor in early 2004, while AMD did the same a year later in their Athlon 64 CPUs.
Although there are likely few pre-2004 PCs still in operation —George W. Bush (remember him?) was in his first term — there are always exceptions.
The restriction does not apply to Chrome running on ARM silicon.