Date: Sat, 04 Oct 2008 14:29:08 +0100 From: Dieter <freebsd@sopwith.solgatos.com> To: freebsd-usb@freebsd.org, 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: <200810042129.VAA24823@sopwith.solgatos.com> In-Reply-To: Your message of "Thu, 25 Sep 2008 21:00:22 %2B0200." <20080925190022.GB93308@cicely7.cicely.de>
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> > Surely a "good" USB to RS-232 bridge (if one exists?) or a RS-232 > > filter/isolator (assuming they exist?) would be *far* less expensive > > than the server class alpha you suggest below. > > It depend on how much RS232 you need and how many slots the OP has free. > Nevertheless a "good" RS232 bridge if needed in number are not cheap > either - ntoe that you can get affordable PCI extenders as well. The PCI expanders I've seen cost almost as much as getting an entire additional machine. > > > > The problem with PCI is the limited number of slots. :-( > > > > > > Well - not realy with server class alphas... > > > > In my world, a "server" means 1-4 full height 19" racks with quite large > > price tags and power&cooling requirements. Some people think a server > > is a pee-cee. So I'm not sure what you mean by "server class alphas". > > Server doesn't mean rack, but beside from a few OEM boards and small > 19" system all alphas have lots of free slots available. > > > I have what I would call a "workstation" class alpha, which cost an > > obscene amount to get 6 PCI slots instead of 4, and at times they are > > all full. So I can't use up a slot just to get a couple more RS-232 > > ports. How many PCI slots does a server class alpha have? > > Well the AS4100 I have already has 8 slots which is not that uncommon > for alpha servers. I'd call an alpha with only 8 slots a workstation class machine. It wouldn't take much to fill up 8 slots. > The real big ones can even have a few hundred slots. A few hundred slots would be server class. And I'm sure a price tag to match, along with floor space, power, and cooling requirements. > > USB to RS-232 bridge could be a good solution, if I knew which > > make&model of bridge worked well with *BSD. Poking around on the web > > I can't even find what chip they have inside. > > Really forget about USB to RS232. > It is not the chip which is the problem it is the principal. > You really need galvanic isolation, because USB can't handle ground > loops, which no cheap device has. > You can use any kind of chip with propper isolation, but then it > is likely more expensive than any other kind of solution. I assume this is marketing driven. Adding a few optos can't increase the manufacturing cost *that* much. Sounds like a market opportunity for someone. > > Do these bridges actually work properly, or do they have gotchas > > like the USB to SATA/PATA bridges? > > The prolific bridges work well enough if you don't have a ground > loop and FTDI chips are better IMHO. Thanks.
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