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David, to calculate how much RAM OS X is actually capable of using, simply open Activity Monitor and add the value you see near Used: with the value near Free: under the System Memory tab in the bottom half of the window. On Unibody MacBook Pros, the sum is never 4 GB as it should be, but somewhere around 3.75 GB. The reason is pretty simply. Apple has allocated the 256 MB of RAM for the 9400 at startup. So, even when you're using the 9600 chip with its 256 or 512 MB of VRAM, that 256 MB of your system RAM just sits there, pre-allocated for the 9400, but doing nothing.
How about opening Terminal and using 'top', there is a section similar to the following;
PhysMem: 504M wired, 1166M active, 156M inactive, 2092M used, 2004M free.
Adding the Used and Free = 4096M.
I would agree that doing as you said that Activity Monitor does show about 3.75, I would rather trust the output of the UNIX feature however. I will check on another OS shortly and report back if results are different.
The problem with using top is that it may just be reporting the actual memory installed, like Activity Monitor's pie chart does. I was looking around the xnu kernel source code and there is a variable called sane_size that is the total size of the installed memory modules and, according to some source code comments is used for "default calculations". There is also a variable max_mem which is what the kernel flag maxmem parameter controls, and it appears to be the true amount of RAM actually useable by the OS, taking into consideration memory used by the EFI and memory mapped I/O.
I just confirmed that, at least on Mac OS X, 256 MB is definitely reserved by the system, likely for use with the 9400M even when the 9600M GT is in use. All you have to do to test this theory is compile and execute the program located here:
When I booted up with no maxmem parameter or maxmem=4100, and ran hostbasicinfo, I got a max_mem value of 3840. Since there is 4096 MB of physical RAM, that leaves 256 MB RAM (4096 - 3840) unavailable to the OS.
When I booted up with a maxmem parameter of maxmem=3456, I got the expected max_mem value of 3456. This means, that with the maxmem=3456 workaround, you're effectively giving up 384 MB of RAM, not 640 MB as you might expect. It still kind of ***** that Apple reserves 256 MB of RAM regardless of what card is in use, but there you have it.
Note that memory_size will always say 2048 MB only because it is a 32-bit value (I'm guessing it is used in the kernel in legacy code).
Interestingly enough, I ran hostbasicinfo on a Mac Mini with integrated GMA 950 graphics. It has 2 GB installed and the maxmem value was 2048 MB. Seeing as how 64 MB of this memory is definitely used by the Intel GMA 950 integrated graphics, I'm thinking that Apple has done something significantly different with the Nvidia platform that they're not even letting the OS get at 256 MB of the memory. Significantly different doesn't mean incorrect, but if it is different new code (either in drivers or in firmware), then perhaps it has yet to have all of the bugs worked out of it.
Ok, I have a feeling the maxmem=4100 doesn't seem to be working. This is going to be a slightly long post so bear with me -
After installing OSX on my new 320gb 7200 rpm HDD(seagate) I had put the maxmem=4100 string in the plist file mentioned above. System was running fine. However, yesterday things went a little downhill. First, while carrying my laptop in my bag, when I came home and took it out, it was running VERY hot, with fans running full blast, and there was no display. I think I pressed the power button for a long time, TWICE before it responded, and then I rebooted. I had smcfancontrol installed, and ran it at 6000 rpm for some time, then switched off the system once it cooled down. I reset the smc thinking there might be a problem, then ran the system as usual, and put it to sleep at night. Today morning, when I woke it up, it hanged within 15-20 seconds. While running firefox. When it rebooted it was running VERY sluggish. I saw the colorful waiting disc in the login screen for the first time! I'm going to try and run it at 4100 for this whole day, otherwise, I'm still in my 14 day period, and will demand that apple replace this system with a brand new one.
HOWEVER - could smcfancontrol have caused any of these problems? Should I try resetting the PRAM? I already did it once before, and it seemed to have no effect!
Is my MBP defective? I want to be very sure before I go to Apple to ask for a replacement.
Check out my post above. When I tested maxmem=4100, it was the same as if you hadn't specified any maxmem at all. So most likely you were observing a placebo effect. I've looked at the OS X kernel source code to verify what's going on and there isn't any sort of tricks going on by just specifying maxmem with a number that's higher than the amount of RAM installed. In that case, OS X will just choose the maximum amount of RAM based on your physical RAM. If you switch to maxmem=3456, then it will limit the RAM, and I have yet to have a random freeze using this setting. You will only be losing 384 MB of RAM by using maxmem=3456 vs not using maxmem. That's because 256 MB is taken away for use on the 9400M, so MBPs only ever get to use 3840 MB of RAM anyways.
Apple's engineers are looking into the bug report that I filed. Other than that, I can't mention any details as they're under non-disclosure.
I have had two random freezes since I tried the 3456-maxmem setting, one with the 9600 on and one without it.
Based on your earlier post I would think we can all hope for an update of sorts that will make the NVidia Chip give up it's reserved RAM when not in use and also remove the crashing issue when it is.
Ok, so after 2 more crashes and frantic calls to apple, I'm taking my laptop back to my retailer tomorrow and will try for a replacement. Will keep you guys posted on what happens next.
This maxmem workaround is a stupid solution to get a 2000$ laptop working the way you paid it to work! Bloody load of crap. Everything else about this computer is downright awesome, it's just these stupid kinks which is really ruining my feel!
Note: I shifted back to the 2gb stock ram modules, and as expected it's working perfecto!
However, if after a few visits, there is no other solution, i'll grit my teeth and accept the maxmem=3456 workaround. There was not even a hint of crash with that, and the computer was running very responsively. I suspect the mamxmem=4100 workaround was all placebo **** you apple!
edit: @xray - seems like you got the one with stock 4gb ram. Why are you even tolerating this? yours is a very expensive laptop, take it back to apple, or tell them to fix it! This is unacceptable - why are users even thinking about tolerating this stuff? If enough people start creating a stink and start returning their laptops, apple will have no choice but to address this issue since it'll become too expensive to continuously keep exchanging fualty systems after a point! Heck, i know i'm definitely going to get my money's worth!
Message was edited by: greyanaroth
xray83, I don't want to be an annoyance, but I'm only asking because at first you weren't sure how to set the maxmem. Are you sure that the maxmem parameter actually was set properly (e.g., when you click on the Apple Menu, in the About This Mac window under memory it should read 3.38 GB)? If so, it's still good to know that you're having these freezes as it means that this maxmem trick may be fixing a symptom of the problem but not the underlying issue. Have you tested your RAM extensively to see if it is defective?
You and greyanaroth should indeed both get into contact with Apple and try to get a replacement. The problem could very well be defective hardware and the only fix for that is a hardware repair or replacement.
you're in fact more of a help than an annoyance! I did eventually find some post in some forum (hackintosh-related i think) on how to set the maxmem flag and it showed the predicted amout of memory available in the About This Mac window.
This is what my com.Apple.Boot.plist looked like:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
Could you recommend a RAM-testing prog? I've found Rember but have also read that it is built upon a possibly outdated version of memtest....
As soon as I finish the paper I'm writing on (can't really turn in my machine in the middle of the process) I'll backup all data and tell the guys at my retailer to fix it.
Thanks and best regards
After running without any freezes for almost two weeks, I tried to go back to the 9400 chip yesterday, and BANG, this morning I had the freeze again. Looks like it's the 9400 chip on my machine. Not good really, since the 9600 chip runs really hot, and the 9400 chip is probably more than enough for me.
Again, I have installed 4 GB ram myself, but I haven't touched them since.
In two weeks I'll go on holiday, and before that I'll have my work send the machine in to apple. It will be interesting to hear what they say.
You know this never occurred to me when I had my 15" 2.53GHz unibody mbp. But it froze on me a few times but I never thought anything of it. I remember after it froze I just hardbooted by holding the power button until it shut off and just turned it back on.
Now I realize that this is the issue everyone on this thread is talking about. Wow and I never thought I had one single issue on my 15" mbp. I sold it off a couple of months back since I didnt really need it but I am sure glad I got rid of the thing.
I'm chugging along just fine on a mac mini right now and imho out of all the lineups and its problems, seems like the best machine hooked up to a 24" LED ACD at this time.
17" has plagued issues especially with its 9600m gt cards and god knows if apple has underclocked it to get rid of the artifact/line issues. The 15" mbp has the freezing issues and the Mac Pro has the oscillating humming sound, occassionally freezing issues and sleep issues as well.
I dont want to spend thousands of $$$ to get a machine that has any of these issues.. so far seems like the cheapest mac minis are the perfect ones right now especially with the 9400m gt in these little beauties can play 1080p materials just fine (of course after you upgrade it to 4gb of RAM and put in a faster hdd of course like I have).
I really really wanted to buy a new 17" mbp or a mac pro desktops.. but the pricings and issues are keeping me away. Very happy with the 24" LED ACD + mac mini combo.
Good luck to you all finding your perfect mac for yourselves!