90s is arbitrary; Xerox Alto was 70s
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I don't know that there was a comparable breakthrough in ICE design
The thing is, you seem to be referring to the years, when something was first invented. But first inventing something and/or demoing a (potentially very) simplistic version of it. Is not the same as being able to (economically), go to mass market with it.
E.g. Take the humble transistor.
The original (1947+) ones, were hand-made, (I'm not an expert on Ge transistors, so could easily be mistaken) Germanium (which didn't seem to make the best of transistors), too expensive (1947+), not really mass-produced (in a big way). Relatively unreliable (1947+), subject to significant thermal runaway problems. Not suitable for higher voltages, higher currents were tricky and max power dissipation was not brilliant (1947+).
They also couldn't cope with much temperature, and would exhibit considerable change in parameters, as the temperature changes.
So, many significant inventions in the transistor world, had to occur, such as Silicon, and various improvements to the manufacturability of them. Took place.
Then it took time for new 'transistorised' circuit designs to be made (developed/invented).
Finally, they had to displace (compete with), the existing valve/tube market players.
So, although technically speaking, the transistor was invented around 1947 (even that is not agreed by everyone, as there may have been other, relevant inventions, much earlier).
It took a number of decades, for them to become commonplace.
Perhaps (opinions can vary), from around 1970 (I know there was transistor items, especially radios in the 50s, and the 60s, had a number of transistorised items, hit the market) onwards, in most things. The transistors really took off.
One could perhaps argue, it took the invention of the integrated circuit, to see transistors really succeed.
I.e. As regards the windows like OS. (Xerox Alto etc). I doubt it was ready in that form to hit the mass market. Affordable, reasonably powerful computers needed to be invented (especially cpus, graphics and memory).
Hard/floppy disks needed to be improved, and made cheaper/smaller.
Then the entire windows eco-system, had to be created, along with a number of key software applications.
That would have taken quite some time.
So, yes. In e.g. 70s, you could have seen a DEMO of something windows like. It was NOT a product, that could have been released in e.g. 1971.
1971 = Memory prices HUGE, just for 1K of semiconductor ram (dram I think).
1971 = 4 bit, 100,000 instructions per second, max memory space 4K, Intel 4004 cpu. (I'm sure windows 10 could fit inside 4K of address space, with a tiny bit of optimisation. N.B. I'm never sarcastic).
1971 = Looking at Mainframe, higher capacity (but still small by today's standards), hard disks. They were huge items, the size of washing machines. Presumably cost millions of dollars. I.e. not really ready to hit the mass market.
tl;dr
Post getting too long. Although 90s is arbitrary, it probably wasn't viable for it to be that much sooner, than it was. E.g. 1971, as shown above. As the stuff wasn't available then and/or was too expensive for the mass market.