Freezing 7200/120

Posted on 1998-08-17
Last Modified: 2010-04-14
I picked up a 7200/120 PowerMac a little while ago for a ridiculously low price on clearance.  anyways, I got it home, set it up and was disappointed to find that it constantly froze after about 5-10 minutes of use.  I searched the net for help and found this question from Experts Exchange:

    I have a 7200/120 that kept on freezing every 5 minutes or so, and I
    couldn't figure why. I zapped the PRAM, ran the hard disk through the
    wringer, did a super clean install of the system, got all the patches.....
    still, no matter what it would freeze up after five minutes every time....

    Then all of a sudden, it's not happening anymore.... the only thing I have
    noticed is that the weather is much cooler now...could this be the
    I hope not, since it didn't really go over 90 degrees, which isn't so hot.
    I remember running my 660AV in Australia and I know for a fact it was  close to 90 degrees
    almost all summer, and even got to 113 degrees...

Like this gentleman, I've tried everything:  Zapped the PRAM, removed the cache, tried a new hard disk, tried a new CD-ROM drive, tried a new keyboard/mouse and even a new SCSI cable.  The only thing I haven't tried is new RAM as I don't have a new chip (but I will try that shortly)

The accepted answer to this problem was overheating, but the fan is working fine and the heatsink on the processor is not even warm to the touch.  The problem however is intermittent enough that it does seem like a hardware problem.

Any suggestions?
Question by:JeremyKalanuk
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Expert Comment

ID: 1536074
You have the AutoStart 9805 Worm (virus). You can find an antidote and information about it at:

Author Comment

ID: 1536075
I've read about the AutoStart worm and its symptoms are not indicative of my problem.  However, I should have mentioned that I am starting the system up with a Mac OS8 CD, then reformatting the disk and then reinstalling the software.  The Mac hasn't even been on the Internet yet.

One point which would support the idea that heat might be causing it is:  When I first got it home yesterday, it was fairly warm outside and the machine would always crash at around 30-90% through on installing OS8.  However, today, after starting the machine up and the surroundings had time to cool down it went through the entire OS8 installation (I must have tried like 15 times yesterday) and didn't crash until it started rebuilding the desktop after the reinstall.

Again, the CPU is anything but warm to the touch however, and the machine still crashes randomly within at least the first 15 minutes of use.  Although I did leave it for around 30 minutes today with no activity and it hadn't crashed.  I suspect I got a motherboard with a bummed 601 processor that overheats considerably too fast.  But that's not what I'm hoping for.

Expert Comment

ID: 1536076
Is there a clock accelerator installed?
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Author Comment

ID: 1536077
Nope.  No clock accelerator.  Although I have made some progress:  I fashioned a makeshift air baffle (a la many Pentium IIs) to run the air from the fan directly over the processor.  This must have cooled the chip down sufficiently as I had about 30 minutes of use or so.  

I took the heatsink off and reseated it, but that didn't make a difference.  

However I think it is now definately a heat issue and I probably got a lemon 601 processor which can't stand heat to any degree.    I spoke to a friend and I'll try to slap some thermal compound and a better heatsink with a fan on top of this stupid thing.

Anybody else have any better ideas?  The processor is soldered onto the motherboard and therefore isn't replaceable.

Expert Comment

ID: 1536078
What config of RAM do you have installed?
I had a very similar problem with my 7200/75 and it was related to the RAM chips being faulty as opposed to the processor.

Expert Comment

ID: 1536079
"Anybody else have any better ideas?"

Sell it or use it for parts. I checked with the Magic 8 Ball...
"Outlook not so good!"

Sorry man, I'm just the messenger...:)

Expert Comment

ID: 1536080
Try a peltier cooler on the processor.  Those things can give your hands frostbite.

I hope this helps.

--MikroData (jkjung)

Expert Comment

ID: 1536081
get the ram chips quick, it is a ram problem.

Author Comment

ID: 1536082
Well, what I ended up doing is I sold it to a friend of mine who has a friend at an Apple Dealer.  He has a friend who can fix it under AppleCare i guess.  I will however let you guys know what the problem was, if its just RAM he's getting a GREAT deal.

Expert Comment

ID: 1536083
Did you buy this machine used? If not, how can you be sure it doesn't have the worm virus? I'd run Eradicator anyway (follow TheHub's advice), just to be sure. The worm will keep your machine goofed and spastic, no matter what you do, unless you kill it.

Accepted Solution

TheHub earned 100 total points
ID: 1536084
I checked with the Magic 8 Ball..."Outlook not so good!"

Sell it or use it for parts.

Expert Comment

ID: 1536085
If he completely reinstalled the machine off the MacOS 8 CD-ROM, then unless the CD-ROM itself is infected with the virus, you can be pretty sure the machine is clean.

I would hope that much was obvious.

Jeremy -- please keep us posted!  This is of special interest to those of us with other members of the 7200 family....

Author Comment

ID: 1536086
Hmm.  Unfortunately I think this machine's logic board is toast.  I've tried replacing the RAM and still the same darn thing.  (although now its gotten even worse and it will basically not do anything beyond come up with a happy-Mac and the processor is cold to the touch: its in my basement, so I don't know if it is heat.)

I think I can just give up and try to throw this thing out the window.

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