The PC (5150) wasn't a "real" IBM design, but was developed externally. Even more so, IBM was quite cautious to not put their more valuable assets on risk by th

The PC (5150) wasn't a "real" IBM design, but was developed externally. Even more so, IBM was quite cautious to not put their more valuable assets on risk by this "small" office machine (a strategy, which eventually came to nothing with the advent of the i386 generation). So there wasn't much "trickle-down" and the 3270 stuff was still dedicated to "genuine" IBM assets. You couldn't even run a 3270 terminal emulation. This required an expensive extra card or later a special XT model. – Just consider this: the 5150 was actually some sort of plan B, where plan A would have been to acquire Atari and sell (a possible somewhat improved version of) the Atari 800 as the IBM PC (there are photos of prototypes for the repackaged design by Bill Lowe [1]). Which may also shed some light on what the original specs for the 5150 may have looked like. [1] https://twitter.com/yesterbits/status/975119004531679232/photo/1 https://twitter.com/yesterbits/status/975119004531679232/pho...