Ah, that is simple. Because Bus speed can hover around 99.98-100.03 mHz, depending on mobo and settings and actual CPU speed is determined from this by multiplier. So it can be 99.98*45=4499.1 mHz. And different tools reports stuff more or less precise.
For HWINFO 99.98 = 100.00 basically, because normal step for BCLK is 0.1 mHz even for top tier motherboards iirc.
Another possibility as there is some another factor that limits max boost clock for this specific core. Like for my cores it can be voltage requested (they likely get to border of their V/F curve even despite offset). But it shouldn't be an issue for 4500 mHz, though. More than that, it only affects effective clock, not nominal clock.
Hi guys, as you can see, then YES 5800X3D can do 4.55ghz all cores in games only BCLK 102.25 C-states & CCPC Preffered Enables in BIOS CO-22