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Consequences of Bad RAM Other Hardware
I recently purchased a used G5 Power Mac (2 x 1.8 GHz with 2 GB RAM) with System 10.4.11 installed on the 160 GB HD. It was bought to replace a Quicksilver which had been upgraded to run OS X 10.5.4 so I naturally wanted to upgrade this machine to 10.5.4.

Upon running the Install DVD using the Archive & Install option, I got an error message stating that "The BaseSystem package was not compatible with this machine and to contact the software supplier." At this stage I did not suspect a RAM problem so proceeded to install 10.5.1 on the same HD using another G5 of the same specs. It loaded OK so I moved the disk back to the "new" G5 and tried to run the Migration Assistant to recover the data files we needed.

The Migration Assistant stalled and, in the process, probably corrupted the bookkeeping file that I most wanted to access. I then suspected that the Leopard Install disk might have been faulty, since that was an implication of the error message. I bought a new Leopard Install DVD and got the same error message. I then tried to install OS X 10.4 from the install DVD but it too produced the same error message.

Finally, I started to suspect a hardware fault, so I found my copy of TechTool DeLuxe on an AppleCare CD. I ran it and discovered that the RAM test failed. I removed all 8 256 MB chips and replaced them with two good 512 MB chips from another G5. TechTool then passed all the hardware and I could proceed with the installation of OS X 10.5.1 and the upgrade to OS X 10.5.4. Three pairs of the 256MB RAM chips have passed the Tech Tool so have used these and will return the remaining pair to the vendor.

Migration Assistant was used to transfer applications, and these appear to have transferred correctly. I have pulled a good copy of the Bookkeeping file from the Time Machine backups that were running on the original G4.

It is now obvious that the vendor of this G5 had not installed OS X 10.4.11 from a DVD but had probably made a clone of the HD before installing it in this machine. It is also clear that they had not tested the RAM before listing this Mac on their web site.

My experience is thus a salutary warning to all purchasers of a used Mac. I just wish the error message that I first received had been a bit more wide ranging and less directed at a possible software issue.

[kirkmc adds: This is less of a hint than a cautionary tale, and a clue for troubleshooting certain types of problems. I've had problems with bad RAM a few times over the years, and especially recall the early days of Mac OS X, which was much more sensitive to RAM than OS 9. I had an iMac DV SE, and installed OS X 10.1 on it. It ran fine for a while, but then would crash or kernel panic. It turned out that I had two RAM cards in it, the second of which was bad; when the Mac needed to access more than the first card's memory, it had problems. Replacing the second card resolved my problems.]
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Consequences of Bad RAM
Authored by: jyu on Aug 18, '08 07:52:03AM

Good story. Thanks for letting us know bad rams can cause an "incompatible" error. Many of us need that to save some troubleshooting time.

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Consequences of Bad RAM
Authored by: Chas on Aug 18, '08 09:45:35AM

It's true, bad RAM can cause subtle and incomprehensible problems that are difficult to diagnose. Even worse, Apple's official hardware test software is almost useless at diagnosing bad RAM. Many third-party diagnostics are similarly useless (like Tech Tool Pro).
I have found the only reliable RAM diagnostic is memtest. It found defective RAM in my Quad G5 that had passed every other diagnostic I could find.

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Consequences of Bad RAM
Authored by: hdms on Aug 18, '08 03:11:15PM

Just as a side note to this: I had a iMac G5 2GHz that would randomly freeze, or panic. I had upgraded the RAM to 2 x 1GB modules. Error log messages suggested RAM as the culprit, so even though TTD and AHT passed the RAM (and everything else) I replaced both modules and still there was a random problem. Turns out it was a case of cooking capacitors causing the trouble - even though the iMac was outside the 'problematic' range and all hardware tests passed. Apple replaced the logic board FOC, and the problem was solved. Until it cooked up the capacitors again a few months later.....

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Consequences of Bad RAM
Authored by: barryjaylevine on Aug 18, '08 09:19:49PM
AHT and TT Deluxe will often fail to spot bad RAM because the methods that are used by those apps to detect bad RAM are not stringent enough. In my experience, memtest always finds bad RAM although one should remember that a bad RAM slot may present itself as bad RAM.

Memtest may be found here:

(No, I have no connection with the author)

Two things in this world aren't overrated: Macintosh and Lemon Meringue Pie.

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Consequences of Bad RAM
Authored by: T0b1 on Aug 19, '08 01:50:37PM
1st off - one can hold D during boot and boot the apple system test from the install DVD. This found the bad ram for me.
Works for me too and its free.

RAM tests during a running system wont work .....

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Consequences of Bad RAM
Authored by: drmacnut on Aug 19, '08 12:25:14AM

I think it is prudent to always run AHT (and memtest if you have the time) on any new machine you acquire. By "new" I mean, brand new or used and "new to you". AHT should, of course, be run as the Extended Test.

Running these tests at least gives you a baseline on the condition of the hardware before you start to use it.

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Consequences of Bad RAM
Authored by: eddively on Aug 19, '08 06:03:34AM

FYI - #1 Cause of failed OS installs is bad RAM. Immediately after any error message during an OS install, always check for 3rd party RAM.

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Consequences of Bad RAM
Authored by: CHerbold on Aug 20, '08 02:18:44PM

This is my favorite tried and true method for detecting bad ram when all other tests pass. I always keep a FireWire drive available to install OS X just for this. Once found I replace with known good ram and installs work flawlessly if RAM is the case, however hard drive issues are high on the list for install issues as well.

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