Newsgroups: comp.sys.next Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mstar!mstar.morningstar.com!bob From: bob@MorningStar.Com (Bob Sutterfield) Subject: Re: Can the Next ports run at 57600 baud RS422? In-Reply-To: rit@killdeer.Stanford.EDU's message of 13 Jun 91 15:24:26 GMT Message-ID: Sender: usenet@MorningStar.COM (USENET Administrator) Reply-To: bob@MorningStar.Com (Bob Sutterfield) Organization: Morning Star Technologies References: <1991Jun13.152426.20007@neon.Stanford.EDU> <1991Jun13.182809.23141@zardoz.club.cc.cmu.edu> Date: Fri, 14 Jun 91 16:14:39 GMT Lines: 60 In article <1991Jun13.152426.20007@neon.Stanford.EDU> rit@killdeer.Stanford.EDU (Jean-Francois Rit) writes: Can the Next ports run at 57600 baud RS422? All I could get from the man pages is that zs can run at any of 16 speeds and that tty speeds are: [50 thru 38400] The highest supported async clock speed, with the standard device driver, is defined in as 38400. I haven't yet tested to see whether they can achieve that in real throughput. If one wished different values than those (higher or lower or in between) then one would need to supply a custom device driver, complete with custom ioctls. The highest sync clock speed we recommend with our X.25 daemon on the NeXT serial ports is 19200, because that's the highest speed at which it runs reliably. We have clocked it higher (e.g. 38400), but it gets more underruns the higher you push the speed. X.25 "works" at those speeds only because of the redundancy of the higher-level protocols, which cause frames to be resent when needed. In article <1991Jun13.182809.23141@zardoz.club.cc.cmu.edu> ddj@zardoz.club.cc.cmu.edu (Doug DeJulio) writes: I'm pretty sure the hardware can do better. The same X.25 daemon code runs reliably at 64K on a SPARCstation-1, which uses the same Zilog 8530 serial interface chip, so yes the hardware can do better. We run X.25 over RS232 (sync) on our VME boards using the 8530 at speeds over 500K, so yes some parts of the hardware can do much better. (You don't want to run RS232 async at very high speeds, because the waveforms begin to get distorted by the capacitance.) Our X.25 daemon's serial interface speed is limited on the NeXT's native ports because of certain design misfeatures of the NeXT Mach 2.* 8530 interrupt service routines. This has been reported to NeXT as a bug. Also, the SPARC architecture is much better at servicing interrupts than is the Motorola 68K found in (today's :-) NeXT. In article scott@mcs-server.gac.edu (Scott Hess) writes: The super-serial chips ... are not supposed to run any faster than 38400, or so I've heard. 38400 is the highest async serial speed found in on any UNIX system I've encountered. The problem is mostly that they are simply older technology (albeit well-proven). The 8530 can run fast just fine. As above, they manage 64K sync just fine in other UNIX systems, when those systems service their interrupts correctly. I've heard various rumors about various devices that _can_ go faster - via the SCSI or DPS ports - but, alas, as shipped Unix can't do greater than 38,400. Our SCSI-attached sync serial interface runs at T1 speeds and better, but it doesn't use the 8530. A serial async device driver either for its ports or for the NeXT-native 8530s could define whatever speeds it likes, but you probably won't get much over 64K async on the native NeXT ports.