Hristo,
The 605DC (96 octane) uses 1.98 ata (59" Hg) to produce 2000 hp at sea level and can maintain that boost up to 5100m.
The 605DB (87 octane) uses 1.8 ata (54") for 1800 hp at sea level up to 6000m. (Note: these figures apply for 605DC as well as boost falls from 1.98 to 1.8 from 5100m to 6000m. Above 6000m, the DC and DB would be identical)
The 605AM uses only 1.7 ata (51") for 1800 hp @ sea level up to 4100m (small supercharger). The larger supercharger draws some extra power from the 605D, which is why the AM can make 1800 hp with slightly less boost. The boost on this engine drops from 1.7 @ 4100m to 1.42 @ 5700m, significantly less than the 605D. For the AS, with increased supercharger, the boost falls to 1.42 at 8000m.