[Gllug] Sun Sparcstation - disconnecting serial console causes BREAK

[Nix]

On Fri, 12 Aug 2005, John Edwards spake:
> On Fri, Aug 12, 2005 at 10:30:16AM +0100, Nix wrote:
>> On Thu, 11 Aug 2005, Ian Northeast suggested tentatively:
> <snip>
>> It's a dilemma. Leave the cable in and PC reboots kill the Sun, and
>> 'cos it's serves all the home directories I have trouble getting back in
>> to do a `go'; take it out and severe buggerups on the Sun are
>> unfixable.
> 
> How are you with a soldering iron ?

My coordination sucks and I have muscle tremors, but I can muddle along;
there are many false starts but things always work in the end. :)

> This is related to the "disconnect causes BREAK", and can be fixed by 

I thought it might be.

> placing a resister between pins 3 and 25 on a DB25 serial connection.

That doesn't sound too terribly difficult. :) Thanks!

> to use one terminal with many machines via a switchbox.  Suggested 
> solutions include a special cable (on a 4/2xx CPU, a 4.7K resistor 
> between pins 3 and 25 may work) or modifying the SunOS serial driver 
> (zs) to ignore breaks.
> 
> At Brunel Uni this was included in a little custom built DB25-RJ45 
> adapter. People like RS will sell DB25-DB25 adapters with enough 
> space for a resister and cables. 

I've got a DB25-RJ45 adaptor (as the Sun's serial port is an RJ45 port,
one was essential), but it obviously doesn't have this. I'll have to get
an extra DB25-DB25 widget and solder the appropriate stuff into it.
(It's not as though I'd notice the extra stacking on top of the gender-
bender, 9-pin->25-pin, and DB25->RJ45 adapter I already have attached
to that line...)

>> FWIW, I've never had a cable unplug send a break; maybe it's machine-
>> specific, or maybe I've just been very lucky.
> 
> I've certainly seen it on SparcStations, maybe Sun fixed this by the 
> time of the Netra.

It looks like they did: part of the point of the Netra was that you
could stack huge piles of them in a dark satanic datacentre and remotely
administer the lot: I had a look a minute ago, and connecting the serial
console cable to a switchbox is the expected usage scenario in the user
guide...

-- 
`I work in computers so, of course, I'm an expert on everything.'
                                                     --- Simon Rumble
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