Re: booting with no keyboard or moue - frying mb

[dman <dsh8290@rit.edu>]

On Sun, Feb 17, 2002 at 11:37:21PM -0800, Osamu Aoki wrote:
| On Sun, Feb 17, 2002 at 07:57:36PM -0800, Alvin Oga wrote:
| > donno... i've plugged and unplugged various mouse and kbs
| > all the time into lots-o-mbs and machines and have not
| > yet fried any mb... ( guess i can consider myself lucky...
| 
| True but if you think about it, it may be true PS@ is dangerous.
| 
| If I remember, PS2 bi-directional I/O lines are open collector output
| and input with pull up registers.  If some static charge hits input when
| unplugging KB, this may cause latch up of CMOS input circuit if
| protection circuit does not work right.  Old cheap CMOS device without
| protection circuit will cause large current shortage between power line
| and ground upon latch up.  Thus toasted MB.
| 
| Modern I/O chips should be smart enough to deal with this ...

Thanks for the detailed explanation of what actually happens.  It is
much more helpful than a repetitive "yes it does" "no it doesn't"
argument.

-D

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