There was another 804x-family member that ultimately became very popular, namely the 8042, which was a microprocessor-compatible peripheral controller. I suspect you're confusing that with the "real" 804x family. It's features and behavior were quite different from the register-related behavior of the mainstream parts. Aside from their rather low performance, the 8042 was pretty handy. There was also an 8044 ("RUPI"), which was a communication controller. I don't believe they were as popular as the 8042, though.

Intel based its GPIB controllers, among others on the 8042. That, I think, is why we "learned" that GPIB was a terribly slow interface channel. It really doesn't have to be.

RE