"Imagine how much power those things used. Every watt of heat they dumped into the room then had to be pumped out, so that means a corresponding amount of air conditioning to take it outside. That seems like a whole mess of juice to me. "
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A 286 used around 3 Watts of power, while a current generation PC PCU uses upwards of 150 W. That's a factor of fifty. That's not even factoring in the GPU's, which these computers would have lacked.
This room was neither quiet or cool. While the CPU's were comparatively low power back then, all the other stuff (modems in particular) would have put out a lot more heat than their modern equivalents. However, this room could realistically have been in somebody's residential home basement without any exotic A/C measures. Maybe a wall-mounted unit or two. It would not have pumped out nearly as much heat or consumed as much power as modern gear of equivalent volume.
Indeed, a single high-end desktop today at full load would probably use more power than everything in that room.
Well, it's truth but not the whole truth.
An IBM AT was capable of consuming nearly 200W [1]. Of course a typical machine would not consume as much, because it did not have its RAM and disk slots maxed out. The CPU indeed consumed around 3W, and normally even lacked a radiator.
A modern PC can consume large amounts of power, mostly determined by the appetites of the GPU. But here is plenty of desktop CPUs with 65W and even 45W TDP, and a typical recent Intel or AMD CPU would consume 3-5W when idle. A quite powerful ARM A7 based system, such as an Orange Pi 5, would draw < 15W under maximum load, likely providing more compute and I/O than that whole room on the photo.
[1]: https://en.wikipedia.org/wiki/IBM_Personal_Computer_AT#Power...