The T-84 is based on the T-80U with a modified all-welded turret. It has ERA on the hull and turret fronts, NBC protection system, a fire-detection/suppression system and GPS navigation. The production (not known) was probably intended for export only and not as an inventory of the Soviet army. Standard T-84 stowes the ammunition in carousel-magazine. The T-84/120 has the ammunition stowed in the turret bustle (see picture).
The autoloader has 22 rounds (in turret) plus 18 stowed in the hull.