That's an excellent question--and goes to the root of the matter, I think. Did IBM intend to create a "home computer" or one that would see proliferation in the business world? I suspect that it was the former view that was held by IBM and accounted for the Florida operation. Had it been with a business aim in mind, the development most likely would have been carried out in New York or San Jose (Santa Theresa). With that view, speed wasn't a concern--and neither was expandable memory. Recall that the 5150 debuted with a memory configuration of 64KB or less.
The "business side" probably surprised IBM; but it shouldn't have. VisiCalc put an Apple into many an executive's office. We offered the standard suite of MCBA minicomputer applications (on an 8085) as well as spreadsheet and word processing. A couple of friends had set up an operation to produce high-end bicycle carrier racks and were looking for an office computer. They wisely bought a Morrow MD3, which came complete with printer and software applications for much less than the cost of a comparable 5150 system--and this was at the same time that I was purchasing my 5150. (I had considered buying the NEC APC, which again, was a much better deal than the 5150, but could find little on the system--it was a "closed" system).
Then there was IBM. They pretty much
had to sell the thing through Sears and Computerland, as they were completely unequipped to sell to minor customers. I recall going to the IBM Sales office on Arques and trying to place an order for five 5150 systems. I was turned over to a sales engineer who didn't have a clue and was informed that we could expect to take delivery of the 5150s in
six weeks. We bought them from Computerland the next day.
Another sign of conflicting vision was the Displaywriter (using an 8086), that was viewed by some IBM management as the ultimate business personal computer. But again, IBM couldn't read the PC world correctly.
this article shows the problem. Third parties couldn't sell the Displaywriter and IBM couldn't sell general-purpose software for it.
As far as buses, we used a modified Multibus architecture, with a few extra lines to enable better communication between certain cards. The rule was that no card should have a cable hanging off of it. All cables to various peripherals terminated at the backplane. But we were 16-bit capable right from the start. S100, being a technically inferior bus, still managed to progress to 16 bits during that time. It was obvious that the 8-bit ISA bus was never going to host 16 data bits.
My view is that IBM never intended to market anything other than a "home computer". The success of the 5150, 5160 and 5170 convinced them that there was a real untapped business market and that led them to bring out the PS/2 series., which really was a tour-de-force, but again, a "closed" system, which was too bad.