Modus... some modem info plz? :-)

[RSI]

I am wondering about modems... and I know that you know quite a bit about them

So, if you could kindly pull up a bit of info..

I basically know the difference between hardware and software modems, I know that K56flex and X2 are DIFFERENT but I dont really know in which ways.. I know that V.90 standardized everything and got rid of compatibility issues... I know that most ISA modems are hardware but there are some ISA winmodems, and most PCI are winmodems but there are some hardware, etc.

What exactly differentiates K56Flex and X2 protocols?

 

[Modus]

3Com (US Robotics) developed their own proprietary x2 standard while Rockwell (Conexant) introduced K56Flex and licensed it widely. They both did essentially the same thing: allow for up to 56Kbps downloads (53k because of FCC regulations) and 33.6Kbps uploads. The technical specifics of each standard are not really important; it's enough to know that the modem pool you're trying to connect with supports your standard of choice. Tests were done by various industry experts and, in the end, the consensus was the standards were basically equal -- x2 was slightly faster while K56Flex was slightly more forgiving of line noise (or vice versa, I can't recall).

Eventually, the v.90 standard was ratified and adopted by everyone. It was supposed to "combine the best of both worlds" from each standard, but really didn't improve performance significantly. Now, v.92 aims to raise the upload throughput from 33.6 to 56k, even with the download throughput. This is not a big deal.

Modern modems invariably support either x2 or K56Flex as a fall-back protocol in case the target modem does not allow v.90 connections. In fact, you can sometimes get slightly better performance (latency or throughput or both) by using a customized initialization string to force your modem to use its "natural" protocol, even if v.90 is available.

Modus