4GB upgrade & Snow Leopard

OK, I can't believe I'm asking this question as I know the answer in Windows, but this is my first foray into 4GB in OS X. Just to appease my TypeA twists, could someone please comment for me?

Upgraded my uMB to 4GB last night and System Memory in OS X Activity Monitor (Utilities folder) shows 3.75GB available. I'm not freaked out about this, just wanting to check my curiosity.

Now the About This Mac pop-up window shows 4GB installed so I'm thinking the difference may have to do with OS memory addresses and such which is why you end up with memory recognition in 32bit windows systems, but I'm hoping for confirmation from others that I'm not missing something. The other possibility I considered for the difference is just simply the 1024bit vs 1000bit thing that you end up with in HDD sizing (and that would actually match nicely with the conversion @ ~3.73GB ).

I'm feeling sheepish .

 

Where are you seeing 3.75 exactly? I only see 4gb on mine looking at about mac, istat...

if you see 3.75 on a PC that's a different story.

 

I'm confused. So in OS X it shows 4GB, but Windows only shows 3.75GB?

If so, that's normal if you're running a 32bit version of Windows(such as XP), as you can index more than that with 32bit memory addresses. Snow Leopard is a 64bit OS and can, therefore, access a whole bunch more memory.

 

Sorry you all, in trying to be clear I appear to have been confusing. I'm not looking at Windows, just the OS X side.

1. About This Mac shows 4GB.

2. iStat Pro, after glancing at it and adding everything up (which is where I first got curious) memory total is ~ 3.7GB

3. Activity Monitor (System Memory tab right next to the CPU one) indicates 3.75GB total memory right below that pretty pie chart with the slices for Wired/Active/Inactive/Free.

The discrepancy of 2x2GB installed and 3.75GB reported in iStat/Activity Monitor is the basis for my question.

I still think this is just a math thing with a simple explanation and I'm only having a paranoid streak, and I'm not in the mood to sit through a memtest run.

Still feeling sheepish..... thx!

 

don't forget the 256mb for the 9400m , that is taken from system memory, even if you run the 9600m GT , I think you still loose it.

 

A-ha, I forgot about that! No 9600 in my little MB, but I do believe you may have solved it for me after all. Those numbers would make sense, unless the gpu dedicated memory was already part of the Wired block (and I don't have my MB with me to check the Wired total)?

 

you have an nvidia 9400m gpu?

256 MB of your system memory is wired to that 9400m (which doesn't have any memory of its own). That memory is not available to your system, and that is happening at the hardware level, beneath the OS. That is why you are "missing" (not really) 256MB.

 

I never noticed but adding up istat does equal 3.74gb for me. the ~256mb missing is definately allocated to the nvidia.

 

as soon as i read this thread and saw you have a 13", i realised it's the dedicated gpu...unfortunately this happens because it it integrated on the mother board..

 

Great - many thx to all in this thread.

--troy

 

Just an additional note: that 256 mb isn't being completely wasted even if you are running the 9600m gt. The 9400m is still accessible as an open cl device. In short- the two graphics cards in your laptop can both accelerate certain apps if you are in performance mode. In battery saving mode, only the 9400m is powered on, so it is the only device usable for rendering / opencl.

 

so does this mean in performance mode, the 2 gpu's are actually working??????

 

not all the time.

if you are running an application built using Open CL and you are in performance mode, then both cores of your CPU, your 9600m, and your 9400m could all be contributing their power for processing.

 

thanks...it the first time i'm hearing about it..+rep

 

OpenCL is one of the major new features in snow leopard. http://www.apple.com/macosx/technology/ It's also fairly new so there is not a crap load of programs using it yet.

 

yeah there's not much taking advantage of open CL right now for consumers.

however, i did want to note that your 9400m is still "on" when you have the 9600m running in snow leopard, whereas if you are running the 9400m, the 9600m is "off". And you can *eventually* expect to get some benefit out of the fact that it works this way.

unfortunately, in windows, apple locked the 9400m to "off" and the 9600m to "on" at all times regardless of whatever you set.