Date: Sat, 29 Jun 1996 16:40:43 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: jparnas@jparnas.cybercom.net (Jacob M. Parnas) Cc: stesin@elvisti.kiev.ua, msmith@atrad.adelaide.edu.au, Kevin_Swanson@blacksmith.com, hardware@freebsd.org, bsdi-users@bsdi.com Subject: Re: muliport boards - building a PPP dialup server Message-ID: <199606290710.QAA20610@genesis.atrad.adelaide.edu.au> In-Reply-To: <199606281741.NAA04008@jparnas.cybercom.net> from "Jacob M. Parnas" at Jun 28, 96 01:41:22 pm
next in thread | previous in thread | raw e-mail | index | archive | help
Jacob M. Parnas stands accused of saying: > > I'm confused. I thought the 16550 was good up to 115,200 baud, but when > ISDN eventually takes over with compression, ~512kbaud will be the norm. > I don't know if they can handle that. I've heard of a 16650 to come out that > can do better. The 16550 can be clocked safely to several megabits/s. The problem with their implementation in the PC is that they're clocked at ~1.8MHz, which limits them to 115k2. The 16650 is a 16550 with a 32-bye FIFO. Neither are suitable for 512KBps; at this speed you have a new byte arriving every 16us, or a full FIFO after only 512usec. This is too fast for anything other than a dedicated system. The best way to do ISDN into a PC is with a $20 ethernet card and a single-MAC ethernet<->ISDN T/A. > Its amazing that one of the slowest protocols on the computer is the > one that gives most people the most trouble. The UARTs seem to be > one step behind as do the motherboard/software companies. I'm of > course talking about RS/232 system, which has been a problem with > some software at anything over 300 baud at times (even with 9600 > baud modems operating at 300 baud. Sun requires a special board at > least on my sparc 2. So there's no problem with a 10mbit/sec > ethernet, but 1200baud to 1/20 of the original ethernet speed is > even on workstations. The problem is one of backwards compatability. There are plenty of UARTs around that work, and work well, at higher speeds. The 8250 however was an egregious crock when it was first released in the late 1970's, and has not aged well at all. None of the better UARTs have achieved sufficient acceptance to make any serious headway. > On the positive side, I'm told that CDA is going to port to BSDI > next for the Sportster 128 Kbaud (512kbaud with compression) and > should have a beta copy in late July. THey've already done it for > Unixware and SCO and possibly Solaris (I think they said they were > finishing it up). Anyway, this is a cheap internal card which you > can read all about on http://www.usr.com/. I've seen it for $319, > CDA said that Bell Atlantic and possibly other companies would sell > it for $199 if you bought it at the same time as ISDN service. Of little or no interest on this side of the pond 8) > PS. If I were basing a business on modems, I'd make absolutely > certain that they all worked at 512Kbaud, at the same time. If > you've ever experienced This is just stupid. Look at the huge installed base of 14k and 28k modems, and the phenomenal cost of ISDN services in most of the world. There's no chance that in the short to medium term things are going to change; and thus making a serious investment in modern modem technology is not unreasonable. > overruns, its not pleasant. Usually the machine kernel panics and crashes > the machine, fairly often, or in clusters. Not much fun, especially when > you have users that have to deal with it, and are justifyably less than > pleased at placing their trust in you. I have no idea what sort of hardware or software you're running that panics or crashes on serial overruns, but I suggest you replace it immediately with FreeBSD-based systems, as they don't. 8) > | Jacob M. Parnas -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] Collector of old Unix hardware. "Where are your PEZ?" The Tick [[
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199606290710.QAA20610>