I think by 75 we at DEC hwe had at least two pin compatible source for UART, While CHester G Bell gets credit for the design, my memory is that Vince Bastiani did the design. That set the stage for having the Synchronus /Isochronous chips built too. Signetics was contracted to do the 2652 based on my lineunt design used in the DMC11 (similar to DP8/e and DP11, but ssi chip count reduced and a good bit faster. The SMC chip was based on Frank Zereksi's DU/DUP 11 design. bob
On Tue, Feb 16, 2021 at 1:04 PM Chuck Guzis via cctalk <cctalk@classiccmp.org> wrote: > > Building floppy controllers from MSI TTL was not uncommon, even after > the debut of the WDC LSI chips, which were initially very expensive. > > Even the bit ordering on some of the early controllers wasn't settled. > You can see LSB-first and MSB-first encoded floppies, GCR, MMFM, hard- > and soft-sector implementations. There wasn't a strong push toward the > IBM implementations (3740/System 3) until the later part of the 70s. > > All of which can make deciphering of the early floppy formats "interesting". > > I was surprised in the mid-1970s on a remote console project that I > managed to find that the CDC engineers rolled their own UARTs from SSI. > Apparently simpler to use off-the-shelf components for a couple-off > project than try to justify a part not in the parts crib already that > may or may not have a second source. > > --Chuck