Anyway, now to the solution of this problem until Apple gets it straight.
First, like every forum I've read on this, if you call Apple Tech Experts, go to a store and talk to sales and/or talk to their 'Geniuses' (I did all of the above before moving to 6GB), they'll tell you the machines 'officially' support 6GB. I more than triple verified and referred to what was published. Their response was that their internal technical publishing has since been updated to 6GB and there is no problem. Moreover, an Expert told me, you can probably get away with 8GB just fine, but we won't warranty or support it past 6GB. Support or warranty? Now why would 6GB be the limit if 4GB is the 'real' limit? They wouldn't - they'd support and warranty it only to 4GB if that was the case.
Before 10.6, 6GB worked just dandy. After the upgrade to 10.6, I saw the issue everyone else is seeing. Both on a 6GB machine and was on my wife's 4GB MBP - identical models, but mine I put 6GB in mine AFTER talking to 4-people at Apple (via the above avenues) about the supported amount as I didn't bother to think to check maximum at the time I bought these. Yes, saw it on her 4GB machine pre-10.6.1.
(I use nvram boot-args="-v" to have a verbose boot-up as well as kernel dumps - it's not as perty, but it is very useful in many ways beyond this.)
Now, after the upgrade to 10.6 on the 4GB machine, she was getting the panics with either Parallels or Fusion running for a while. I haven't put her on a 64-bit kernel yet (still). Once hers was updated to 10.6.1 the problem went away. When she was running into it, I didn't bother doing anything or looking deeply - I know the reality of initial releases. They can't possibly test the same as the masses can. So, I figured sit tight and it'll be addressed quickly. I did. It was. This is probably why you don't see many complaining with machines that have the max 4GB 'officially supported' hardware. Most people I know updated after 10.6.1 was released.
Now, onto my 6GB machine. I upgraded to 10.6 later and 10.6.1 was already available. The upgrade went no problem. 10.6.1 and all the various other upgrades: no problem. I promptly set it to boot 64-bit kernel (to avoid holding down 6+4 - I'd tell you how, but don't want this censored for being off topic 🙂. After working with the machine on/off for about a week (my primary OS is Linux on another laptop - I like OS X as well so it is my secondary for email/calendar/ms office/etc.), I started seeing the kp's. Then I became obsessed with determining the issue. I wrote some quick C progs and after a few days I found the issue. I'll say I found it on my machine since I have no way of determining how this will work on others. But, I suspect it will. I did tell my buddy about it who was having the same issue: solved his problem as well.
For reference on how well this has worked now for over a week: I have had multiple Parallels (5 beta) VMs running (Win7 64, WinXP, Ubuntu) simultaneously, a FF browser with usually 10 or more tabs open plus another window, Safari, Entourage, Mac Mail, Address Book, Live Mesh (oh yeah, I love it and use it), Time Machine backups, iTunes and usually a few terminal windows all running on different spaces. That's my typical running routine. Every since I've made the change I'm getting to: ZERO problems.
One thing I can say with beyond a high-level of confidence is that it's an issue with 10.6 (both Kernels and wasn't an issue in 10.5), which is why I periodically search to see if Apple has caught on yet. I spend enough time hacking Linux kernels and more years than I can remember on both Linux and BSD that I don't ever quite understand why flattening a machine and reinstalling is recommended - well, unless it's Windows or there are too many apps/variables to deal with. My point is, I'd rather get to the root cause, get it fixed and move on so that I never see it again; or if it comes up again, I can quickly solve (usually).
So, I encourage everyone to send the OSX automated log dumps to Apple as you receive them if you haven't been. Further, if you haven't, before making this change, grab at least another couple kernel panics and send the log dumps. This accomplishes two things: 1) allows Apple to see the issue on proper scale, 2) informs them what the problem is (easy to see if you study them - patterns built).
Finally, the fix, or workaround I should say, is easier than you might think: use the 9600M GPU (i.e., system preferences | Energy Saver | choose "Higher Performance" - logout, login, restart for good measure). My guess is the kernel will panic a few times on you before getting it straight.
Why? Because the 9400 uses shared memory and the amount adjusts with the amount of RAM. Wait, dude, are you saying you found that 10.6 isn't properly adjusting when you go over 4GB? In a way - I won't get too far into details on my supposition, but that's essentially it. See, it's not truly shared, but supposed to be reserved, BUT there is clearly a problem with a bounds overrun. The 9600 uses
dedicated GDDR3 - no shared system memory - hence why no problem.
Further, this might give you an idea of why 10.6 introduced a pervasive flicker problem when using the 9400. Was it me, or just too psychedelic to work on for longer periods? I read about it some time ago in 10.5.n, but never experienced on 3 of my MBs and my MBP, my wife never did nor anyone I knew. However, it's on all of 10.6's now if you put it to sleep and raise the lid and get to work.
Why bothering mentioning this? This fixes that issue as well until it's addressed in 10.6.2 (that's the plan anyway). You may have tried some of the other workarounds or fixes (I warn you on these - could cause file system issues and will remove a lot of your defaults), but a hack when clearly, based on these two issues, 10.6 is not playing well with either the late 2008s or more current MBPs and their integrated GPU chipset (9400).
The config is NOT ideal as the machine runs hot, eats the battery and I don't need it (many don't even those who think they might - unless you do HEAVY graphics and/or gaming, the integrated chip works just fine).
So, is it
really the amount of RAM? Not from where I sit. Brand? Nope. Pairing? Nah - that's just to ensure dual channel is available - if not, it goes single (though go with a paired set since single hits performance and heck if you need OWC to do that). Bad batch? You know how extremely rare this is? I have bought commodity memory since 286 (and prob. 8088, but don't recall) and built all my own computers a couple per year. Then worked in a DC assembling Proliants, installing IBMs/Dells/Rackables in the thousands - HDDs, MBs and RAID controllers were the #1 issue - never RAM. I can only recall over the last 20-years finding a bad memory module 2 or 3 times. Easy to detect on a PC, apparently not an Apple?
Now that I have this sorted, I might actually throw in 4GBx2 just to see what 8GB does. Oh yeah, pushing the memory limit and THEN, only then, can you lecture me 🙂 I suspect, that is where hardware limitations kick in.
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