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Unread postPosted: Sat Nov 15, 2014 11:51 pm 
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So as some may recall I bought a Tezro from a local recycling company a few days ago. An interesting thing happened on the way to powering it up; the power button got all balled up inside its little recess and it couldn't pop back out. It's a bad design even by SGI standards (picture below), if you push the button in farther than the thickness of the skin it resides in there's nothing to contain it from flopping this way or that and getting trapped behind the skin. Now why, you may ask, did I push the button in so far? You have to in order to get the power to come on! The button assembly has both the on and the reset button, and they reach out through snaky lever arms to actuate the microswitches that actually do the work (also pictured below). The button assembly is held to the skin by a screw on one end, and the levers reach out from the other end. Note in the other picture that there's also an NMI microswitch that does not have an associated lever arm, so the only way to access it is to remove the skin. I'm assuming for no good reason that NMI stands for "non maskable interrupt," and I say for no good reason because I can't think of a good reason why you'd ever need to send a non maskable interrupt from a front panel switch. But then I'm no expert on interrupts, maskable or not. Perhaps the computer scientists among us can provide enlightenment. With no further ado, the pix:


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Unread postPosted: Sun Nov 16, 2014 12:18 pm 
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Here's a pic of the switch screwed into the skin. The skin has two part numbers, one molded in and one on a paper tag. The molded number is 050-0875-002 REV A and the one on the tag says 013-3899-003 REV. A, B1584 Bermo Inc 3103, who were no doubt the molders.


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Unread postPosted: Sun Nov 16, 2014 1:05 pm 
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vishnu wrote:
I'm assuming for no good reason that NMI stands for "non maskable interrupt," and I say for no good reason because I can't think of a good reason why you'd ever need to send a non maskable interrupt from a front panel switch. But then I'm no expert on interrupts, maskable or not. Perhaps the computer scientists among us can provide enlightenment.

The NMI button is indeed used to send an NMI interrupt, which allows the IRIX NMI handler to capture the state of all the processors and gracefully shut down the system (NMI aren't recoverable, at least on Octane and Origin families). The system user's guide usually describes where the NMI button is, with a mention that it should only be hit upon explicit request (and guidance) from a Silicon Graphics' support engineer.

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Unread postPosted: Sun Nov 16, 2014 1:12 pm 
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miod wrote:
vishnu wrote:
I'm assuming for no good reason that NMI stands for "non maskable interrupt," and I say for no good reason because I can't think of a good reason why you'd ever need to send a non maskable interrupt from a front panel switch. But then I'm no expert on interrupts, maskable or not. Perhaps the computer scientists among us can provide enlightenment.

The NMI button is indeed used to send an NMI interrupt, which allows the IRIX NMI handler to capture the state of all the processors and gracefully shut down the system (NMI aren't recoverable, at least on Octane and Origin families). The system user's guide usually describes where the NMI button is, with a mention that it should only be hit upon explicit request (and guidance) from a Silicon Graphics' support engineer.

Thanks I knew someone would know! :mrgreen: I have the Tezro user's guide but haven't gotten very far into it yet. No doubt I will eventually have it memorized... :lol:

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