The ultimate 'Quick Computer' flex was BeOS back in the '90s. It was running on a BeBox with two PowerPC 603 chips at 66 MHz (later 133, but I'm certain I saw this demo in the 66 era).
I saw it demoed at MacWorld (January 1996 I presume), and they did the following demo:
1. They spun up a bunch of apps: played video, rendered 3D, etc. The BeBox had two sets of LEDs on the front that reflected CPU usage, so you could see the load increase.
2. They would keep loading apps until both meters were permanently pegged: 100% CPU usage on both. This was something like twenty windows, mixed across a bunch of tasks.
3. They would grab a single window -- say the 3D render -- and drag it rapidly around the screen. You would see the 3D render immediately speed up as it came to the foreground, and all other tasks slow down noticeably as the Be rep dragged the window around the screen. The window moved smoothly.
4. Then, they would disable one processor, leaving one to support the load that had sat two at 100%. Everything on screen became very slow, except the foreground 3D render, which still moved with reasonable speed.
5. They would again grab a window -- maybe a video this time -- and drag it rapidly around the screen. Every other window slowed to a crawl (but didn't stop). The video window moved around the screen smoothly, and the video kept playing smoothly as well.
All this to say that BeOS knew who it served: the user with their hand on the mouse. You clicked a new window, that window immediately received enough CPU to be responsive. Give the OS a loony task, and it would still do its best to prioritize whatever you told it was important.
I have never seen an OS before or since that handled multi-tasking as well.
But wow, playing with an OS that is conceived as a whole product, with coherence in UI and paradigms. I haven’t felt this since the 90s.
Of course it’s pretty limited by the absence of application ecosystem but everything you’ve got is pretty clean. And it runs fairly well on a relatively modern computer for a niche OS.
Haiku is lovely, but it is considerably bigger and slower than BeOS was. It's also vastly more feature-complete and has 10x the apps, but it's not as miraculous in performance terms, not by a long chalk.
Haiku has both a "serverless XLib/X11 compatibility layer" [0], and a similar wayland one that takes Xlib or wayland API calls and translates them into Haiku API calls.”[0] so a lot of GTK+/Qt apps have ports [1], and the Epiphany browser(webkit) runs so you can use web apps.
e.g. Libre Office, Inskcape, Gimp etc.
*(edit) also it has WINE, so some 64 bit windows apps.
I'm not sure how stable or full featured these are.
I think a big low hanging fruit on windows at least is to make single programs asynchronous to be more tolerate to various delays.
I.e. if you open a folder it should not wait until every single hard drive has spun up to be responsive. What if all I want is the recent access top option loaded from NVMe?
I have a USB hub on Windows with several portable hard-drives attached to it. I started feeling very slowed down when taking backups while trying to do something else at the same time. I am using Acronis for backups. Then I tried removing one of those portable drives and everything is much better now.
Somehow a single "bad" USB drive seems to be able to slow down the whole Windows-machine.
I had a preFCC certification BeBox. It had the dual 66mhz PPC 603 chips.
Lemme tell ya: the dual 66 was NOT a quick computer lol. Maybe earlier than R5 BeOS was on it but by R5 it was a dog. The dual 133 faired better.
The biggest issue was that the 603 wasn't an SMP capable chip on its own. The GLU chipset could either run one 603 + L2 cache or both 603s with only L1 cache. Coherence was done in software.
I usually ran mine with just one cpu active, sadly.
The author also designed the "Spring '83" protocol, which is a really quirky, neat way of disseminating information in a small way i.e. like classifieds in a newspaper.
I saw it demoed at MacWorld (January 1996 I presume), and they did the following demo:
1. They spun up a bunch of apps: played video, rendered 3D, etc. The BeBox had two sets of LEDs on the front that reflected CPU usage, so you could see the load increase.
2. They would keep loading apps until both meters were permanently pegged: 100% CPU usage on both. This was something like twenty windows, mixed across a bunch of tasks.
3. They would grab a single window -- say the 3D render -- and drag it rapidly around the screen. You would see the 3D render immediately speed up as it came to the foreground, and all other tasks slow down noticeably as the Be rep dragged the window around the screen. The window moved smoothly.
4. Then, they would disable one processor, leaving one to support the load that had sat two at 100%. Everything on screen became very slow, except the foreground 3D render, which still moved with reasonable speed.
5. They would again grab a window -- maybe a video this time -- and drag it rapidly around the screen. Every other window slowed to a crawl (but didn't stop). The video window moved around the screen smoothly, and the video kept playing smoothly as well.
All this to say that BeOS knew who it served: the user with their hand on the mouse. You clicked a new window, that window immediately received enough CPU to be responsive. Give the OS a loony task, and it would still do its best to prioritize whatever you told it was important.
I have never seen an OS before or since that handled multi-tasking as well.