The MCS6501, a first and very rare member of the MOS Technology 65xx CPU family.
Introduced in 1975 with the MCS6502 to MCS6505, pin compatible with the Motorola 6800 and, after legal issues, not produced afterwards.
The (preliminary) datasheet of August 1975 is the only document where the 6501 is documented
Another article from the Dutch KIM Kenner magazine: RECORDING PROGRAMS WITH THE KIM-1 AND THE CASSETTE RECORDEROrigin...
Stephen Crozier made a clone of the Unilab Three Chips main board.
Thanks to Mathias Ohlerich for the scan of the Sonderheft 2
Dave Williams, who designed and builds the MOS KIM-1 Reproductions, sent me three worthwhile documents: - Schematic - ...