GPIB(general purpose interface bus), AKA HPIB(Hewlett-Packard Interface Bus) or IEEE-488, was(is) used for industrial and scientific equipment. It actually predates desktop/personal computers. It's actually a really elegant interface-it has 31 addresses available, and for being quite an old interface has surprisingly little latency(although it's not super fast). The connectors are usually hermaphroditic, and can be stacked if needed to daisy chain multiple devices. My "best" is 5 separate devices off one computer, although I know people running more(in GC-MS applications, you can have 3 separate HPIB devices for one instrument, and a single copy of the software can control up to 4 systems).
I've dealt with quite a bit of scientific equipment that uses it, although these days all I deal with is older Hewlett Packard gas chromatographs and mass specs. AFAIK, HP/Agilent and National Instruments both manufactured interface cards. The HP cards I've used have all been either ISA or PCI, while I have NI cards in NuBus, ISA, and PCI. Obviously, as you've found, they made some other configurations. As a side note, HP/Agilent and NI both made USB interfaces.
Also, as another interesting note, Hewlett Packard/Agilent stuff in my experience will ONLY work with HP/Agilent brand cards, and not with NI cards. Most other stuff I've dealt with, including Varian GC-MSs and a few other odds and ends was set up with NI cards, and I've never had a reason to try them with HP cards(which cost a fair bit more on the secondary market). The HP cards say "HPIB" on them, while NI cards will say GPIB. Also, of small note, the last couple of systems I've built have been Dell Optiplex GX620s/Win2K running HP MSD Chemstation G1701BA. That particular model has come into favor among the independent techs maintaining older HP stuff as it's at a sweet spot of running Win2K nicely but also uses SATA so we can put new HDDs in it rather than being at the mercy of a dwindling supply of IDEs(remember this stuff in many cases runs 24/7, or at least will run 5-6 days a week often for 16 hours, and the data it collects can be priceless). That particular computer, though, will only work with an Agilent 82350B PCI card, not the older HP 82350A version. The Agilent version is marked GPIB.
I know I'm getting way off topic, but I'm currently bringing an HP 6890/5973 GC-MS back to life for my current employer. I'm working on a shoestring budget(I'm buying some stuff out of pocket) and as I type this, I'm installing Win2K on an older Dell tower. Even though I have a few Optiplexes GX 620s squirreled away, the 82350Bs are rather expensive, so I'm building this one with an 82341 ISA card from my stash(the computer already has an 82335 card in it, but that's no good with the version of software I'm using). I'm hoping at the end of the fiscal year(next June) to get the $6K to upgrade this to LAN communication, which opens up the available supply of computers a whole lot and also lets me run the newest version of MSD Chemstation G1701EA E.02.02 on Win10.
Probably more than you wanted to know, though
. It's hard for me to take a stab at what it would operate. There were SOME instruments that ran on Macs, or had Mac versions of the software, but not many. Most older stuff ran on UNIX(typically Solaris, which I'm not sure ever ran on Macs) while more recent devices usually run on Windows.