Comparing the whole system against an actual task is the only way to really measure - everything else, including the clockspeed, is marketing.
https://en.m.wikipedia.org/wiki/Advanced_Micro_Devices,_Inc.....
My claim is that (1) results on irrelevant benchmarks like SPEC do matter for CPU sales (probably not for big tech companies that operate their own datacentres – they’ll likely do their own testing – but likely for many ‘savvy’ consumers and also for companies that want to market their computers as having fast CPUs) and (2) the complicated world of benchmarks is handled very poorly by the people who tend to evaluate CPUs with them and publish their results.
Edit: found it - https://en.wikipedia.org/wiki/Performance_Rating
The problem was that the CPU clock speed levels categorising your system as high/mid/low performance were quite obviously based on Pentium 4 clock speeds, even though at the time AMD actually had a market share of around 40 – 50 % for desktop computers. This meant that everybody with an AMD processor would find his/her performance and graphics settings mysteriously restricted. People using the first generations of Intel's own Core i-processors had similar problems if they were still playing those games a few years later.
The saving grace was that at least things weren't totally hard-coded – things were controlled by a rules file in a plain text-based format, and so it was comparatively easy to just change the expected clock speed levels to something more reasonable for a non-Pentium 4 processor.
This was also useful because the GPU detection had its own share of problems down the line – I still occasionally play Sim City 4, and for some reason or other on my current system the game doesn't correctly detect the amount of video RAM I have and therefore resorts to extremely restrictive fallback settings unless I manually override it, and AMD recycling graphics card model numbers also caused some confusion that had to be manually fixed.