SMD disk interface pinout/specs

Jeffrey Sharp wrote: i think you may be referring to the normal density and high density versions. If I recall original SMD had about 26K / track. EMD drives from CDC had twice that. density. The main thing that was a problem was that there was originally a chip that would do CRC generation in the original 7400 series IC line. This chip in the same circuitry could not keep up with the higher speed SMD and demanded a newer chip. I recall that most designers went with ECC chips in newer designs, rather than the original CRC, as a result of newer logic on the market then. Our original design at a company I worked for was out in around 1981 or 1982. If I recall the newer SMD designs were out around 1984 or so. We did not support them due to having a very small market to support, and low demand for further updates. Jim