On 2026-08-09 14:04, Dennis Boone wrote:

> Is it a coincidence that the connectors look a lot like a scaled-down
> IBM channel connector?

I'm not familiar with a channel connector that's anything like the
common micro-ribbon (Amphenol series 57) connector often used for
GPIB and Centronics printer interfaces.

The PET end didn't use a standard connector; it was a card edge, 0.1"
pitch I think.

Sorry, I got two images mixed up in my mind; indeed, the stackable 2-pin Amphenol connectors is what I have on the programmable RF attenuators in
my lab at work.

Unfortunately, another picture popped up in my memory at the mention of
GPIB: A rectangular connector roughly 25 x 35 mm with pins in multiple
row, where every other row is offset half the pin distance. The
photograph in my mind probably has somewhere around 35 pins. And now I
have no idea where I remember seeing this. And as I look up the bus and
tag connectors on the IBM channel on Wikipedia, they don't look like
that either.

I did get to play with attaching IBM style peripherals to a VAX Unibus
via a Z80 microcontroller back in 1984 or so, when I wrote the Z80
program to drive a Xerox 9700 printer from the VAX. But not having
written channel programs for an actual S/360 machine, my mind was not
nearly twisted enough to understand the need to support certain devices
like a 2703 communications controller, that was heavily dependent on the
TIC (Transfer In Channel) channel commands. All my device could do was a
crude selector channel, that could drive a printer or a tape drive, or probably (though we never got to try it) a disk drive.
--
Lars Poulsen - an old geek in Santa Barbara, California

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