Path: utzoo!mnetor!uunet!husc6!purdue!kyw
From: kyw@cs.purdue.EDU (Ko-Yang Wang)
Newsgroups: comp.arch
Subject: Lights on computers (was Re: Cray architecture)
Message-ID: <3671@medusa.cs.purdue.edu>
Date: 29 Mar 88 04:27:44 GMT
References: <7762@alice.UUCP> <418@ole.UUCP> <3216@phri.UUCP> <1574@osiris.UUCP> <1461@ut-emx.UUCP>
Sender: news@cs.purdue.EDU
Reply-To: kyw@cs.purdue.edu (Ko-Yang Wang)
Organization: Department of Computer Science, Purdue University
Lines: 27
Keywords: LED, parallel computers.

In article <1461@ut-emx.UUCP> reeder@ut-emx.UUCP (William P. Reeder) writes:
>
>I have suggested to many sales reps that they need a bank of gee-whiz
>lights on the front which blink faster as the load goes up.  That way
>people who walk by our machine room and look through the big window
>could see something "impressive".

The Pringle parallel computer (a 64 processor non-shared memory parallel
computer that we designed at Purdue during 81-83 to emulate the CHiP
architecture) does have several banks of red and green LED lights on it.
(actually there are 128 of them, a pair of red and green LEDs for each PE)
We programed the system so that a green LED lights up when the PE associated
with it is doing I/O, and a red LED lights up when that PE is interrupted or
finishes with its computation.
When the Pringle starts to run, the red and green lights start to blink.
I still remember when we successfully ran the first program on it,
we turned of the lights in the room to enjoy the beautiful light show.
(We repeated the execution several times just to see the lights.)
Actually, we used the light pattern to detect deadlocks, when all the green
lights stop blinking for longer than couple minutes and not all red lights
light up - we knew we had a deadlock.
This trick helped us to detect quite a few deadlock situations.

>-- Wills
>William {Wills,Card,Weekly,Virtual} Reeder	reeder@emx.utexas.edu

Ko-Yang Wang