16 Feb
2021
16 Feb
'21
11:07 a.m.
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 at 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