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pwg 2 days ago

Intel also released both the 8086 and 8088 as 40pin DIP's.

Squeezing four more address pins in would have meant multiplexing four more of the pins on the chip, and if you exclude power/ground pins there are only 13 pins that are not multiplexed, and several of those either can't be multiplexed (because they are inputs, i.e., CLK, INTR, NMI) or would have made bus design even more painful than it already is for these chips.

The 4 bit shift, instead of 8 bit shift, for the segment registers was likely as big an address bus they could do that would also fit the constraint of "fits into a 40pin DIP".

https://en.wikipedia.org/wiki/File:Intel_8086_pinout.svg