On Fri, Dec 13, 2019 at 11:10 AM Al Kossow via cctalk <cctalk@classiccmp.org> wrote:
> ANSI has a spec, X3.91M_1987 I don't know if it covers the SMD-E , etc. > X3.91M-1987 section 6 covers "Interface Extensions", which includes adding tag 4, 5, and 6, dual-port provisions, spinup sequencing, index mark and sector mark signals, fixed-head addressing, service voltages on round radial cable, and extended cylinder addressing. I think some of that came in with SMD-E, but I'm not 100% certain. X3.91M-1987 describes data rates of up to 24 Mbps, which came from SMD-E. SMD-E is apparently defined by CDC document 64712402, which I've never been able to obtain.