Starlink. I don't think there was any kind of low-cost satellite uplink/downlink available back in 2000. Probably there were military things available, or perhaps things for shipboard applications, but nothing like a cheap satellite groundstation you could set up to get an internet connection in remote areas, where you don't have any landline. There are isolated parts of the uk countryside that are still not cabled up, where people use starlink today.
Starlink is still not as cheap as broadband or 4G/5G routers here, but very useful if you live somewhere remote.
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And in a similar vein, 4G and 5G networks, being able to use a smartphone as an access point, and dedicated routers using the mobile network. This is a common 4G router available here, for example; they can be very useful when you don't have a broadband connection available. The 5G ones are fast enough to provide a real alternative to broadband.
View: https://www.youtube.com/watch?v=i1cyjljh-wg
Neither of those options were available back in 2000, you only had an internet connection where you had a landline phone line. So we now have other options to get online in more out-of-the-way places.
The whole smartphone area is much more developed now too. The first iphone was launched in 2007, and android came along some time after that. I think back in 2000 I had a dumb motorola phone, it's hard to remember. And of course tablets. So there's been a lot of change in the area of mobile devices. And going along with that... ARM are much larger now than they were in 2000, their low power processors have been a great success in that space. It remains to be seen whether ARM chips will get any mainstream presence in PC's, apart from Apple of course. 25 years has seen the evolution of multiple generations of semiconductors.
And, talking about hardware again, we have seen a lot of convergence of PC electronics with the kind of electronics used in smartphones, you really see this in modern ultra-thin laptops. This macbook air motherboard looks far less like a traditional PC motherboard and much more like a tablet or smartphone mainboard, for example. Whereas back around 2000, the tech was still somewhat separate, PC electronics still looked like PC's and phone electronics was somewhat different technology.
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