It was a safety net designed to prevent operational error.   Naturally, there are limits.  

It was a quaint implementation on the 3b2.  I think that’s the gist of discussing it anyway. 

However, you can see how the 3b2 designers stressed about a user having to deal with an operating system that required care in understanding that you can’t just remove power.  Rather, an orderly shutdown were required.  

If you want to yank the plug, by all means, have at it.  But, I can tell you that I suspect you are the exact type of user that the 3b2 designers felt they were up against in designing this obviously over engineered hardware. 

Of course, your point is a good one. Especially, since countless UNIX boxes at the time had nothing more than a good old power switch that truly was akin to yanking the power cord—-thus, procedures must be followed. 

Yet, it’s still cool that the 3b2 has that little integrated power feature that most fondly remember.   (Maybe I am on the wrong channel, this is TUHS, right?)

It might be worth noting, nearly every UNIX box today (even x86 hardware) has some variety of this power feature today.    So, clearly the 3b2 was ahead of its time (along with a few other vendors)

One last point,  I have an original NCR minitower UNIX box.  This box had a unique feature where it’s solid state RAM would be backed up by a battery. The registers were saved.     So, if you yanked out the power cord, the system would pick up right from where it left off.  Of course, all of the terminal users would need to redraw their screens.  But, this box was immune to yanking out the power cord.  If you wanted to reboot the kernel, there is a procedure to start from scratch.  


Bill Corcoran 

On Jul 1, 2018, at 8:55 PM, John P. Linderman <> wrote:

So prohibiting someone from pushing a button differed in what way from allowing them to pull a plug? I can understand there may have been some difference in state when/if the machine was rebooted. If I just wanted the machine to cease sucking power, what's the difference? I never wanted that box to exist, or come back to life, in whatever color.

On Sun, Jul 1, 2018 at 8:20 PM, William Corcoran <> wrote:
No! no! no!  The 3b2 was one of the first supermicros to fully integrate power management with the system.   Yanking the cord would be unthinkable mainly because it was unnecessary.  The shutdown script would remove power to the the system once the system safely went down and buffers were flushed.   You could also depress this massive rocket switch on the side of the unit and it would kick off the powerdown script.  It is noteworthy that the 3b2 power switch was stateless...allowing human and computer to turn off the power.  

Finally, the 3b2 is probably the only system in the world with system diagnostics so in depth that they were nearly as significant as the operating system.   It’s a telecommunications thing.   Interestingly,  the color of the 3b2 was similar to a VAX Brown and White.  

On Jul 1, 2018, at 6:24 PM, John P. Linderman <> wrote:

Puns aside, anyone who didn't consider pulling the plug was probably not someone who should be bringing the system down.

On Sat, Jun 30, 2018 at 10:17 PM, Greg 'groggy' Lehey <> wrote:
On Saturday, 30 June 2018 at  7:15:07 -0400, Norman Wilson wrote:
> Ron Natalie:
>   My favorite 3B2ism was that the power switch was soft (uncommon then, not so
>   much now).   I seem to recall that if the logged in user wasn't in a
>   particular group, pushing the power button was a no-op.   You didn't have
>   sufficient privs to operate the power.
> ====
> Surely you mean the current user didn't have sufficent power.

Or was experiencing too much resistance?

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