Chinese-all-day-breakfast/MD/g1-3.md

都不 vs. 不都

都不 indicates a complete negation whereas 不都 shows a partial negation:

他們都不忙
    None of them is busy.
他們不都忙
    Not all of them are busy.
我們都不是大夫
    None of us is a doctor.
我們不都是大夫
    Not all of us are doctors.