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.

[Dieter]

> > 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.