Brian's Mail list account <bglists@...>
Here is what you are pointed at if you do an update check when running on an Athlon or Sempron which has no sse2 support in its instruction set.
Your hardware is no longer supported
If your computer has a processor older than Pentium 4, Firefox version 49 and above is no longer supported.
If Firefox is already installed on your computer, you can continue using it but you will not receive updates beyond version 48. If you download Firefox version 49 or above and try to install it, you will see the message, Firefox cannot be installed. This version of Firefox requires a processor with SSE2 support.
Like many programs, newer versions of Firefox require a processor that supports Streaming SIMD Extensions 2 (SSE2) for better security and performance. We recommend a computer with a Pentium 4 or newer processor that supports SSE2 to use the latest version of Firefox, which has more features, stability and security.
Firefox Extended Support Release (ESR) will continue to work with older processors but will not receive updates beyond ESR version 45. Firefox ESR version 52, scheduled for release in March 2017, will no longer be supported.
Clear as mud in many ways, but from the AMD standpoint its clear enough. One supposes the second part of this might well point at operating systems like xp and Vista.
Time marches on of course, and I suppose keeping track of special code to use different routines on very different processors and operating systems must be a minefield in itself.