Why reg conusmes more time than reghdfe in running regression on panel data?

I have two codes below

Code:

reg dep_var indep_var i.unit i.period

and

Code:

reghdfe dep_var indep_var, a(unit period)

I saw that it takes only 5 seconds to run the reghdfe but it takes more than 10 minutes to run reg command above.
Can I ask why this phenomenon happens and how to deal with it (reducing the time running reg command)?

Thanks in advance and warm regards.

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