Which processors does the HP EliteDesk 800 G4 TWR support?

The HP EliteDesk 800 G4 TWR supports only 8th Gen Coffee Lake processors — i3-8100, i5-8400 through 8600, i7-8700 and 8700K, plus Xeon E-2100 series parts. It cannot fit 7th Gen Kaby Lake or 9th Gen chips because Intel changed the pinout with Coffee Lake, and HP’s Q370 chipset enforces that line strictly.