You just don't imagine, how huge landfills are, and how small was number of computers in 1980s.
I mean, in 1980s, only first world seen computers in large quantities.
In 3rd world, computers was exotic until late 1990s or even 2000s.
So for example, China have not desktop computers culture, they jumped from analog culture to smartphones.
In some countries like Russia, computers before middle 1980s was toys for military, because they gives magic possibilities, like make supersilent submarine screw.
Large share of first world computers of 1980s-1990s, was "donated" to countries of 2-3 worlds, because first don't want to pay for utilization, and others are agree to got new for them technology "for free".
Important thing, that old-new technology means, it will not have official support, no spare parts, no upgrades, so large share of old computers become donors of old parts for other old computers.
Only in 1st world, people pay really much attention, to save history, to make right collections of old tech, which are alive, not just static empty cases.
And old tech does not survive without care.
So you could assume, 99% of old computers which not so fortunate to become part of some collection, are now dead.
For archeology, I'm in Ukraine regularly talking with collectioners and with engineers, and even now with military, who now regularly got pieces of Russian hardware from 1960s to current.
In many cases it is just impossible to figure out something more than approx time period, when piece of hardware made; in some cases could re-engineer what hardware done.