01-09-2012, 08:57 AM

Reported on here over a month ago that my 27" iMac was repeatedly freezing up. I'd run fsck and it would repair itself but would soon freeze again. Was advised on here to back up system and get hard drive replaced.

I purchased a back up drive and have now had a new hard drive fitted but problem has returned though not quite as bad in as much as I can now work for some hours before it freezes whereas before it could have been as little as 20 minutes.

As well as the system freezing (even force quit didn't work) also would get a dark translucent screen descending and dialogue box saying I need to restart my computer. I understand this indicates a kernel panic. David Pogue says this is almost always related to some piece of add-on hardware.

Could this be my Netgear Router which isn't actually working too smoothly (often needs to be reset, especially after computer has been inactive for long periods). Doesn't seem likely as it often used to freeze whilst using photoshop and not engaging internet). However i can't think of any other add-on it can be. The add-ons I have are an Apple keyboard and mouse, a Canon Pixma printer, an Iomega ego back up, and the Netgear DG834N router.

When it freezes and I run fsck it reports System was modified then says there were several 'Orphaned or Unlinked files'. Jettisoning Kernel Linker. Resetting IO catalogue.

I've started up from System CD and run repair on hard drive and repaired permissions.

I've noticed that when it freezes now several lines appear across the screen - like scratches.

Any thoughts before I'm forced to take it back to the local repair place (They repair Macs but are not official apple repairers)?

(This iMac was one of the first 27" intel macs. the original hard drive was replaced just within the 3-year Applecare period. The model identifier is iMac6,1. It has i intel core duo 2.33GHz processor.)

01-09-2012, 05:51 PM

Freezing is almost always caused by a hardware error but it can also in lesser cases be attributed to bad software.

Hard drive, memory, graphics controller, are all likely causes of freezing. If you recently replaced the hard drive, it would be unlikely that the new hard drive is likewise at fault although I would not rule that out.

01-09-2012, 07:01 PM

Thanks chscag for replying.

Is there any way I can test for a hardware fault? Can I use Disc Utility? This problem is getting expensive and I don't want to fork out for Disc warrior or whatever if I can do it with what is available.

Under About This Mac/More info/Hardware/Diagnostics it says Apple Hardware Test, Last Run: 18/09/4009 08:08, Version 3A113, result: Passed. What is this? can I run it again? (Is 18/09/4009 a mistake for 18/09/2009?)

01-09-2012, 07:05 PM

Run the Apple Hardware Test again. Let's see what it says even though the tests themselves are not conclusive and sometimes miss stuff. See this link.

01-09-2012, 08:28 PM

I ran the Apple Hardware Tests several times. It took 9 seconds to detect an error and issue an ALERT.
Printed error code, 4MEM/1/40000000:587c6000 or similar each time.

I notice that it now says Test FAILED in About this Mac/Diagnostics.

Can I find out what this error code signifies and whether I can do anything to fix it?

01-09-2012, 10:23 PM

OK. That's looks like a memory module test failure. But still not as conclusive as we would like to see. Let's make sure. Download and run the free "MemTest for Mac" from here.

Let us know what the results are.

01-09-2012, 11:47 PM

https://discussions.apple.com/thread...art=0&tstart=0

01-10-2012, 01:50 AM

Yeah, it certainly looks like he has some bad memory in his machine Dennis. The memtest program I suggested he download and run will confirm it if indeed the memory is acting up.

01-10-2012, 08:40 AM

Apologies chscaq for not replying sooner. I'm in England 6 hours ahead of Texas (8 hours CA Dennis) and my last message was at 1:30 AM.

Ran MemTest

Last login: Tue Jan 10 11:24:18 on ttys000
richard-barness-imac:~ barn$ memtest all 9

Memtest version 4.22 (64-bit)
Copyright (C) 2004 Charles Cazabon
Copyright (C) 2004-2008 Tony Scaminaci (Macintosh port)
Licensed under the GNU General Public License version 2 only

Mac OS X 10.5.8 (9L31a) running in multiuser mode
Memory Page Size: 4096
System has 2 Intel core(s) with SSE
Requested memory: 2497MB (2618548224 bytes)
Available memory: 2497MB (2618548224 bytes)
Allocated memory: 2497MB (2618548224 bytes) at local address 0x0000000101000000
Attempting memory lock... locked successfully
Partitioning memory into 2 comparison buffers...
Buffer A: 1248MB (1309274112 bytes) starts at local address 0x0000000101000000
Buffer B: 1248MB (1309274112 bytes) starts at local address 0x000000014f09f000

and it produced pages of FAILURE reports.

Typically-

Compare SUB :

FAILURE! Data mismatch at local BUFA address 0x000000011f8cf000, BUFB address 0x000000016d96e000
BUFA Data: 0x088607f7aa99affb, BUFB Data: 0x088607f7aa99aff1

Conclusion-

*** Address Test Failed *** One or more DIMM address lines are non-functional.
Execution time: 1084 seconds.

Many thanks for pointing me in this direction.

Can I fix this myself? Could the memory chips just need re-seating? I've put memory chips in my Quadra years ago but doesn't the imac need an Apple tech?

01-10-2012, 03:10 PM

Many thanks for pointing me in this direction.

Can I fix this myself? Could the memory chips just need re-seating? I've put memory chips in my Quadra years ago but doesn't the imac need an Apple tech?

Yes, you can certainly repair it yourself. Replacing memory modules in an iMac is an easy do it yourself project. As for reseating, you can give that a try if you wish but I recommend just replacing both modules.

Memory right now is inexpensive and may be a good time for you to upgrade while you're at it. I'm not familiar with who sells memory in the UK, but some of our UK members have purchased memory on line from Amazon UK. But I'm sure you'll be able to find suppliers closer to you rather than wait for shipping to arrive.

Let us know how it turns out.

01-10-2012, 06:27 PM

I have an account with Amazon UK. Crucial seems to be biggest for Mac memory here.
When I purchased this computer in 2006 Apple had just produced the first 27" intel imacs. I ordered it to be assembled by Apple and opted for the bigger, better Ram, video card and whatever was offered (apart from hard drive). So the 2.33 GHZ processor wasn't the standard. Is this why I cannot find this actual model on either Apple or Crucial's list? According to them this model, imac 6.1 is a 24" whereas mine is 27". I assume it doesn't matter as long as I replace the memory with what was there.

Apple give 3GB as maximum for this model (2GB and 1 GB). If I put in 4 GB (2GB and 2GB) can it cause any problems or do any damage?

01-10-2012, 06:36 PM

According to Apple your machine can accept 4 GB (2 x 2 GB modules) but only 3 GB will be addressed. I would go ahead and use the 2 x 2 GB modules.

01-15-2012, 05:24 PM

Many thanks chscaq, or can I call you ch? (sorry English joke)

Installed two 2GB modules and it's been OK for last four days. Ran memtest again and 2 hours later (as opposed to the previous 9 seconds) it dave the all-clear.

(There was a slight problem identifying the right modules as the company didn't cater for a 27" 2.33 GHz iMac from late 2006. When I checked my serial number with Apple they've got me down as owning a 24". clearly this is one of those times when size doesn't matter).

So I'm up and running. Thanks again.

01-15-2012, 09:08 PM

That's great. Glad to hear you're up and running again. Have fun and visit us often. As we say in Texas: You'all come back, hear?

01-15-2012, 09:39 PM

Next time I'm in Texas the tequillas are on me!