Date: Mon, 15 Dec 1997 05:22:43 +0000 From: Jeremy McMillan <aphor@horizon.ppp.ripco.net> To: freebsd-isdn@FreeBSD.ORG Subject: [Fwd: What kind of serial card should I use with ISDN and FreeBSD] Message-ID: <3494BEA2.238F2F07@horizon.ppp.ripco.net>
next in thread | raw e-mail | index | archive | help
This is a response to a question not specific to FreeBSD or ISDN, but is more about connecting high-speed serial devices (in gerneral) to PCs. Peter Haight wrote: > I just got an ISDN line and I'm using a 486/33 with FreeBSD on it to route > our internal network to the outside world. Anyway, my 486 has a 16450 UART > serial card. My understanding is that there are many limitations to this > kind of card and I am wondering what my options are in terms of upgrades > that work with FreeBSD. The 16xxx number refers to the type of FIFO buffer chip (UART) that takes data from your computer's processor and pumps it out a serial port interface. Higher numbers mean later standards and higher speeds. A 16450 will not accept any more than 9600bps. A 16550 will take 57600 bps at a time, and later UARTs will allow higher speeds on up. > The ISDN adapter I'm using is a 3Com ImpactIQ and it says that with > compression it can get speeds up to 230kbps. I'm getting about 85kbps with > it now. In general, compression is advertised at about a 2:1 ratio, and thus I'm guessing your TA has 2 "B" (data) channels at 64Kbps each. Your computer can't even use the bandwidth of one of these channels at 9.6Kbps. Your serial port is a major bottleneck. > The 3Com ImpactIQ came with advetisements for serial cards with 16750 UARTS > on them. Do these work with FreeBSD? Does anyone have any opinions on them? You need one to get your money's worth out of your ISDN line. Get one, but shop around. If you had bought an internal TA, it would have had it's own UART built in. If you bought an ISDN router, you could have just plugged the thing into your favorite ethernet port and you'd be practically up and running. You took the hard way, and now you have to worry about adding a serial card with all of the address line/IRQ/DMA problems associated with it. I hope your 486 is cooperative, though you will likely get it working without unreasonable pains. BTW: Pay extra for a good IEEE certified serial cable rated for 230+kbps. The higher the rated speed the better, since you will have a royal pain in the neck if your cable introduces data errors. --- Jeremy McMillan | Finger for PGP Pursuant to US Code, Title 47, Chapter 5, Subchapter II, '227, any and all unsolicited commercial E-mail sent to this address is subject to a download and archival fee in the amount of $500 US. E-mailing denotes acceptance of these terms.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3494BEA2.238F2F07>