[p3n1s]

56k was not relevant for point to point communicating between arbitrary points on the network though. 56kbps dial-up worked in an asymmetric fashion with a fully digitally connected modem on one end (eg the ISP). Station to station analog modem standards capped out at 33.6k.

> DSL isn't really fundamentally different from a 56k

There's a great deal of additional integrated digital signal processing to make DSL work that was too costly for consumer modems at the time. I wouldn't agree with this assessment. And other than operating on phone lines for last mile it is completely different on all the layers and uses completely different equipment.

> 56k hit a wall because circuit switching has fundamental disadvantages. Packet switching allowed us to get past that.

There were circuit switched networks far faster than 56k, so not sure this had much to do with any inherent limitation.

Packet switching has obvious advantages for network utilization and was a necessary evolution but I don't think it is relevant to any 56k limit or the revolution in DSP that make multi-megabit over copper pairs possible.

[jeffbee]

As you said, the DSP revolution was not scientific it was economic. They always knew how to do it, for decades, but it was unholy expensive. VLSI economically enabled DSL but it was a thing that they knew they wanted to do, and knew how to do, for decades. DSL technology was perfected before the 56K modem was even invented.

[p3n1s]

> They always knew how to do it, for decades

Unless we're limiting to the purely theoretical this is quite the hyperbole and in that case applies equally well to the 56k modem.

Size and heat are also factors. The process nodes did not exist in the 70s and early 80s to produce the integrated circuits necessary. VLSI technically enabled DSL.

The idea that somehow the difference between 1960s integration and 1990s is "purely economic" is pretty silly. If only they threw trillions of dollars more into research in the 60s would we have had the Intel Pentium then rather than 30 years later, maybe, but that is a useless line of reasoning. Someone has to actually do the "science".

You need to actually design and produce a suitable line card equivalent for every subscriber that will support DSL speeds without taking up the space of an airport for it and the cooling. That didn't exist for decades before DSL was rolled out (which started barely a decade after it was patented).

> DSL technology was perfected before the 56K modem was even invented.

Considering that DSL standards continued to evolve after the 56K modem was obsolete this is also hyperbole.

The other thing not yet mentioned which is pretty fundamental is that DSL eschews the 3.3khz bandwidth of POTS.