[belthesar]

With my v.92 soft modem, I was able to regularly connect at 48k, and sometimes 53.3k. I never connected at theoretical max of 56k.

Worthwhile to also mention that ISDN was full duplex, instead of half-duplex like dialup. The modems on either end would need to time-slice to allow bi-directional communication, which in a TCP laden world like the web meant that every interaction was orders of magnitude more latent than on ISDN, in which you had symmetrical, full-duplex 56k of bandwidth between you and the ISDN modem. That's the biggest reason why you had a significant decrease in latency.

[icedchai]

I also vaguely remember there being FCC power limitations on (some?) 56K modems, limiting them to ~53K max. Also, even with a 56K connection, upload speeds were still limited to 33.6K max.

Fortunately, I got cable internet around 1997 and never looked back.