On 2016-Oct-13, at 10:39 AM, Jim Brain wrote: > I thought the question about the prevalence of .156" connectors in early > systems was interesting and I assume someone here has the detail on the > rationale. > > Jim > > -------- Forwarded Message -------- > Subject: CBM edge connectors pitch? > Date: Thu, 13 Oct 2016 19:31:47 +0200 > From: silve...@wfmh.org.pl > Reply-To: cbm-hack...@musoftware.de > To: cbm-hack...@musoftware.de > > Do we know what is the norm used in the CBM edge connectors? Like the IEEE, > USER PORT or CASSETTE? > > I found out mentions that it uses a 0.156" pitch. Where the heck does that > come from? Nothing "round" in either metric or imperial.. > -- > SD! > Message was sent through the cbm-hackers mailing list
The 0.156" is presumably the oldest PCB edge connector, I have an example in tube equipment going back to 1959. Very common in all sorts of equipment through the 60s and 70s. As Tony suggests, it matches up with 5/32" spacing, just as 0.125 is 1/8". Where the rounding of the 1/4 thou (0.00025) took place - in the name or the implementation - I'm not sure.