The first BMW M5, based on the E28 5 Series, made its debut at Amsterdam Motor Show in February 1984. It was the product of demand for an automobile with the carrying capacity of a saloon (sedan), but the overall performance of a sports car. It utilized the 535i chassis and an evolution of the engine from the BMW M1. At its launch, the E28 M5 was the fastest production sedan in the world.
The M5 was equipped with a variant of the M88/3 called the S38 B35 which was equipped with a catalytic converter, which, combined with slightly lower compression of 9.8:1 versus 10.5:1 for the M88/3 reduced the power output to 282 hp. The S38 also differed from the M88/3 in that it had a dual-row timing chain as compared to the M88/3's single row timing chain.
Source: Wikipedia, 2012