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Comment by mikewarot | Hacker News Reader

Nitpick - Baud rate refers to the number of symbols sent by the modem per second, you can't send more than 8000 symbols per second through an analog phone line, as they are sampled at 8 Khz. You can sent multiple bits per symbol, which all modems did. By utilizing a direct digital connection to the phone network, an ISP could send up to 53 kbits/second using all 8 bits of each sample, minus a few for transitions that weren't allowed because of cross talk with other phone lines.

Thus, the fastest modems were 8000 baud.

PS: Yes, it was amazing to see the text actually flow / smooth scroll up the screen for the first time in my life, way faster than I could read it when it got a US Robotics Courier HST modem.

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Ah... memories of technical arguments past. :-)

Some clarification for those who might not be familiar:

One way to illustrate the difference is to consider communicating with physical signal flags, where there's a limit to how fast you can raise and lower the flags. The baud rate is how fast you can change the flag. The bit rate is how fast the information flows.

Say you have only a black flag and a white flag, and you let the black flag be 1 and the white flag 0. In this case, the baud rate and the bit rate are the same, as each flag transition represents 1 bit of information.

Now suppose you have also have a red flag and a green flag. You could let white be 00, black be 01, red be 10, and green be 11. The baud rate (rate of running the flags up and down the pole) remains the same, but the bit rate (number of bits encoded by a flag) has doubled.

Analog modems used all kinds of tricks to encode more than one bit on each symbol transition. Later models sometimes even had built-in data compression and error correction (e.g. the Telebit modems, which would actually simulate things like ZMODEM and UUCP g protocol to the computers, while using their own compression/correction mechanisms on the physical link).

Hehe yeah... 2400bps modems ran at 1200 baud. 33.4Kbps modems ran at 3400 baud (at most)

57600 baud (V.92) to be precise.

8000 Baud (Symbols/second)

According to the spec[1] for the "analog modem" (the one in your office, house, etc)

  6.2 Symbol rate

  The upstream symbol rate shall be 8000 symbol/s derived from the digital network.

1 - https://www.itu.int/rec/T-REC-V.92-200011-I/en

57600 baud is incorrect. It was 57600 bps which was achieved over a 3200 baud connection by utilizing sophisticated signaling and compression.

https://tldp.org/HOWTO/Modem-HOWTO-23.html

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