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8GB RAM on M3 MacBook Pro 'Analogous to 16GB' on PCs, Claims Apple
(www.macrumors.com)
This is a most excellent place for technology news and articles.
You're comparing single channel performance to entire system performance.
That statement simply means the most highest of the high end Mac has 16 memory channels (admittedly more than EPYCs 12, but EPYC is in the ballpark). The mere mortal entry M2 has two channels, just like almost every desktop/laptop grade x86 CPU. They are not getting 800 out of only 8Gb of modules.