[prashnts]

Long time reader of your blog, thanks for doing what you do!

So I've been into "connector technologies" (if that's a thing) for a while -- more specifically I really admire the simplicity of edge connectors that nowadays are basically free (except the higher amount of metal than traces, (gold?) plating etc.). Anything you'd like to add about these sort of connectors from this era? Were they reliable in mating-cycle sense? Could you just casually insert them or was there a specific process? Was there a standard?

As you can see I don't have a precise question, I'm looking more towards the considerations that an engineer at that time would have to take into account. Unfortunately it's not very easy to google this these days.

[kens]

The IBM 1401 team analyzed the gold on the SMS card edge connectors and found they have 100 microinches of gold, which is a lot by modern standards: http://ibm-1401.info/SMS_Tabs_IBM_Report_Dec2007.pdf

The connectors were generally reliable; I don't think we've had any problems with them. You could clean them with isopropyl alcohol if necessary. There was one IBM manual that described a process for removing SMS cards where you'd put a punch card on either side of the board to protect the board against catching on neighboring boards, and then use a special puller to remove the board. But we just pull the boards out by hand without problems.