Date: Thu, 25 Sep 2008 14:58:54 +0200 From: Wilko Bulte <wb@freebie.xs4all.nl> To: ticso@cicely.de Cc: Dieter <freebsd@sopwith.solgatos.com>, freebsd-alpha@freebsd.org, freebsd-hardware@freebsd.org Subject: Re: alpha/127248: System crashes when many (7) serial port terminals (vt320-vt510) connected to the server via com to usb adapter and 2-usb hubs. Message-ID: <20080925125852.GK59387@freebie.xs4all.nl> In-Reply-To: <20080925125417.GQ93308@cicely7.cicely.de> References: <20080920125414.GS93308@cicely7.cicely.de> <200809201655.QAA10313@sopwith.solgatos.com> <20080925125417.GQ93308@cicely7.cicely.de>
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Quoting Bernd Walter, who wrote on Thu, Sep 25, 2008 at 02:54:17PM +0200 .. > On Sat, Sep 20, 2008 at 09:55:59AM +0100, Dieter wrote: > > [ -hardware@ list added to existing -alpha@ thread as this > > doesn't seem to be alpha specific ] > > > > > This is because USB is absolutely crap for this purpose. > > > RS232 terminals, especially with long cables, can produce several kind > > > of spikes and ground loops, which USB is very very sensitive about. > > > > Many things about USB are crap (thanks, inthell), but if a USB to RS-232 > > bridge cannot handle normal spikes and ground loops, I'd blame the > > bridge, not USB itself. If the problem is spikes and ground loops > > there is probably some RS-232 filter/isolator available to clean them > > up. There could be a bug in the bridge which needs a software workaround. > > In any case the system shouldn't crash. > > > > Are there specific make&model USB to RS-232 bridges that people > > have had good luck with? > > USB can't handle spikes and ground loops. > As said: use isolated devices, so you don't have the loops and spikes. > You can blame the device for not being isolated, but you expect every > device to provide expensive workaround for a design failure. > USB is designed for cheap stuff - that's all about it. 20mA current loop comes to mind > > > A galvanic isolated USB device might work, but there are lot of PCI and > > > Ethernet devices on the market which are more solid by design than USB. > > > > The problem with PCI is the limited number of slots. :-( > > Well - not realy with server class alphas... Yeah... a Turbolaser running a terminal server 8-) > > Does anyone make firewire to RS-232 bridges? > > Or stay with the old DEC devices - they are rock solid even after all > those years. DECserver900 are indeed rock solid. Run reverse-telnet driven bij conserver on FreeBSD. Works like a charm. I still have a considerable # of lines like that running in an engineering lab. conserver runs on Tru64 in that particular case. Wilko
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