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The 1801BM3 is single chip microprocessor, was designed in the second half of 1980-th and had PDP-11 compatible architecture. Notable, it was not an exact clone of one of original DEC processors, but had its own internal architecture.
The 1801BM3 is the futher development of 1801BM1/1801BM2 and is the most performance microprocessor in 1801 series.