Let's do a thought experiment.
Let's assume we just never got hard drives to work all that well, head crashes are common and large storage capacities are only possible in servers with incredibly expensive anti vibration setups and what not and there's no way they'd ever work in portable devices. And optical media just didn't work out. Maybe somehow we didn't discover the science in time and the companies working on it just failed or bad management decisions killed off the research into it before anything useful came off of it. And flash storage just never came down in price.
How far could we have pushed cassettes and tape if all the effort that went into other technologies had to be put into cassettes because there simply wasn't a good alternative for data storage. What are the limits of how fast we could move tape in a cassette? How miniaturized would the technology be by now in 2023? I know that there are contemporary tape backup systems with large capacities but there hasn't been any efforts into high speed seek times or making cassettes a viable tiny medium for use as removable media on PDAs or mobile phones.
If we could pack data densely enough and move the tape quickly enough how possible would modern computer tasks like high resolution digital video or image editing be? Assuming that we still had the high speed processors and non-persistent memory of the present but just no other data storage medium aside from magnetic tape.
For inspiration consider that in 1992 we had NT Cassettes that are about as big as an SD card an could store nearly a Gigabyte and in the enterprise LTO-9 tape (released in 2021) stores around 18 TB. So it doesn't sound impossible to have tiny cassettes with a lot of storage if we spend the last 3 decades working on it.
Do we really need our modern data storage for mobile phones? Mobile phones for sure would be very very different than our modern smart phones but mobile phone networks don't sound impossible. Of course the internet would have to work very differently too, but maybe routing and forwarding could be done just with everything from RAM?
A simple mobile telephone could happen maybe, I should have written SMART phone - I just hate that term.
I think the furthest a cassette-based phone you could fit in your pocket could go is text messages. Definitely no apps or browsing a robust website with images
You could probably carry some apps on individual tapes with you? If it was all miniaturized enough and we can cache some things. Digital photos and videos would work too as that obviously has been done many years ago.
If you have to carry separate cassettes it's beyond pocket-sized. Cassettes can only get so small since the spool has inherent thickness to it. I'm thinking the device would have to be bigger than the original gameboy
NT Cassettes were about the size of a full size SD card and maybe twice as thick and that was in 1992. Imagine what 31 years of research could have done to that technology!
I think if Sony could put a disk drive on a PSP it’s not too far fetched to store apps on a cassette.
The PSP drive isn't a traditional disk drive, it's a modified minidisc.