[This article was first published in the July, 2010, issue of
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Gen Ritter writes:
I can’t remember ever reading about kernel panic in any of your letters, which is ok, but you might want to think about writing about it.
Is this a possibility: My Sony Vegas Platinum Edition 9 won’t print to tape to a Sony camcorder. So I exported it to QT format *.mov and brought it over to my G-5.
It said that the mov file was 39.7 MB/second (FCP number in Browser). Opened QT Player, opened the *.mov file, exported to DV Stream, thinking that this would get it to the correct 3.6 MB/second. It did not. It was 6.9 MB/second in a mov file. So all at one time I had QT Player open with the 39.7 MB/second file, QT Player open with the 6.9MB/second file, FCP open with the 6.9MB/second file in the TL (played great in the viewer, produced a red line in the TL) and Viewer. Before I could even render, I got a kernel panic.
I took the computer to the Apple Store where I bought it Just heard back. They said my memory 2GB was bad, they wanted to know if it was third party ram. So I attached the receipt (sent to you, also) that showed it was Apple Ram and exactly what kind.
I think what happened was I asked the OS to use too much RAM at one time and it tried to do it and then I burned it up. Can this be true?
Larry replies: Thanks for writing, Gen! It is always good to hear from you.
Can it be true that you “burned up your RAM loading too many movies into QuickTime?” No.
Can it be true that your RAM is bad? Yes.
A kernel panic is a complete crash of the operating system – probably the most serious software crash that exists.
As the Apple Store intimated, kernel panics are generally not caused by a single application, but by the interaction between the software and hardware. I can completely believe that bad RAM could cause this.
Having multiple files open in QuickTime – even the different formats you mention — should not strain your system so as to cause a crash. Rather, I suspect that some portion of the RAM failed.
However, I’m troubled by the video file created by Vegas that’s 39.7 MB/second. There is no SD video format with that data rate. Nothing even close. DigiBeta, which is the largest SD video file format, only runs at 26.5 MB/second.
I think Vegas is creating files that may be part of the problem as well.
UPDATE – Aug. 10, 2010
Robin Harris adds:
In the question about kernel panics: if you suspect there may be RAM problems you can go into About This Mac > More Info > Memory and OS X will tell you the status of each DIMM. Now, if the status says there is an error, don’t panic! There are many transitory errors in RAM and it is highly likely that a reboot will restore the DIMM to the OK status.
But if a reboot doesn’t restore the DIMM to OK status, you probably have a failed DIMM. Many 3rd party DIMMs have lifetime warranties, so check with your vendor.
Apple’s internal DIMM tests may not find every problem. If you still suspect RAM problems you can download Memtest for about $2, boot into single-user mode, and run it for a more complete test.
The good news is that on a Mac Pro you have Error Correcting Code (ECC) memory, that detects and corrects single bit errors. But iMacs and MacBooks don’t have that, so you can have memory errors and the system won’t know, leading to possible file corruption or application failure.
As it happens, memory errors are a lot more common than expected. See my ZDnet article, “DRAM error rates: Nightmare on DIMM street” at www.zdnet.com/blog/storage/dram-error-rates-nightmare-on-dimm-street/638 for the results of a Google/Carnegie Mellon large-scale study of DRAM error rates.
Larry replies: Robin, thanks.
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