How to enjoy All your RAM

[IceMacMac]

I have been getting completely opposing and conflicting opinions about the need to boot into the 64-bit kernel to access more than 32 GIGs of system RAM (I have 48 GIGs installed).

If I see in "About this Mac" that there are 48 GIGS installed does that insure that my system can access all of it?

I am currently booted in 32-bit kernel and my "About this Mac" does report seeing all 48GB. Does this end the debate/discussion?

After encountering constant crashing while trying to run with the 64 bit kernel, I returned to the 32-bit mode and was surprised when I saw (w 10.6.7) that all my RAM shows up.

 

[S.B.G]

To know for sure if the OS is utilizing all of your RAM, check the Activity Monitor and it will tell you there. For example, I have a non-unibody MBP (pre-Santa Rosa) and it has 4GB in it, About This Mac shows 4GB, but Activity Monitor shows that the OS only recognizes and uses 3GB of that 4GB RAM.

P.S. The attached photo is of my iMac not my MBP I described.

 

[IceMacMac]

It looks like I got a definitive answer from Other World Computing:

Quote:
To utilize over 32GB of memory in your Mac Pro under 10.6.x or greater, you must boot into 64 bit mode. In 32 bit mode, all installed memory will show in system profiler but only up to 32GB will be actively used by the computer.

 

[Aniday]

I booted into the 64 bit kernel but Activity Monitor is saying it's only using 3.75 of the 4 gigs I have installed in my early 2008 MBP.

I'm a little confused.

 

[IceMacMac]

I booted into the 64 bit kernel but Activity Monitor is saying it's only using 3.75 of the 4 gigs I have installed in my early 2008 MBP.

I'm a little confused.

Don't be needlessly vexed. You have zero reason to boot into 64 bit kernel if you only have 4 GIGs of installed RAM. The question only comes into play if you have more than 32 GIGs installed. I advise you to go back to 32 bit kernel and enjoy fuss-free operations.

 

[Aniday]

Don't be needlessly vexed. You have zero reason to boot into 64 bit kernel if you only have 4 GIGs of installed RAM. The question only comes into play if you have more than 32 GIGs installed. I advise you to go back to 32 bit kernel and enjoy fuss-free operations.

The funny thing is everything is working fine in a 64 bit kernel. I'm not running into any compatibility problems.

Why, when Snow Leopard is so far along, hasn't Apple made 64 bit booting default?

 

[IceMacMac]

The funny thing is everything is working fine in a 64 bit kernel. I'm not running into any compatibility problems.

Why, when Snow Leopard is so far along, hasn't Apple made 64 bit booting default?

Apple's 32 bit kernel can run 64 bit apps just fine...so there isn't a big impetus to worry about it.

64 bit booting IS default on the 2010 Mac Pro and will be default in many future Macs. But there are lots of drivers (for RAIDs, PCI cards, etc. etc) that break things. That's exactly what I'm bumping up against and trying to resolve.

My first few days were gleeful running the 64 bit kernel. Then I started having lots of problems. If you suffer my fate...just go back.

I've got 16 GIGs of additional RAM at stake. You have little to gain.

 

[Aniday]

Apple's 32 bit kernel can run 64 bit apps just fine...so there isn't a big impetus to worry about it.

64 bit booting IS default on the 2010 Mac Pro and will be default in many future Macs. But there are lots of drivers (for RAIDs, PCI cards, etc. etc) that break things. That's exactly what I'm bumping up against and trying to resolve.

My first few days were gleeful running the 64 bit kernel. Then I started having lots of problems. If you suffer my fate...just go back.

I've got 16 GIGs of additional RAM at stake. You have little to gain.

Wouldn't the drivers have been updated by now considering the walled garden Apple has set up? Because if not, that's pretty stupid.

 

[Guiyon]

I booted into the 64 bit kernel but Activity Monitor is saying it's only using 3.75 of the 4 gigs I have installed in my early 2008 MBP.

I'm a little confused.

Most likely that unavailable 256MB is the shared memory used for your graphics card.

 

[3soteric]

I have a mid 2010 macbook pro 13", and run that in 64bit mode constantly with only 4gb of RAm - no issues at all with it so far

 

[S.B.G]

I booted into the 64 bit kernel but Activity Monitor is saying it's only using 3.75 of the 4 gigs I have installed in my early 2008 MBP.

I'm a little confused.

It's because of memory overlap...

The MacBook Pro Core 2 Duo presumably uses Intel's 945PM chipset, which can physically handle 4 GB of DDR2 RAM. However, a number of items must be stored in physical RAM space, and when RAM reaches 4 GB, there is some overlap.
In other words, in a 3 GB RAM configuration, there is no overlap with the memory ranges required for certain system functions. Between 3 GB and 4 GB, however, system memory attempts to occupy space that is already assigned to these functions. For instance, the PCI Express RAM allocation occurs at somewhere around 3.5 GB of RAM and requires 256 MB of RAM. Thus, the virtual space between 3.5 GB of RAM and 3.75 GB of RAM is occupied by PCI Express data. So in a system with 3 GB of RAM, nothing is being wasted because the memory space required by PCI Express is still between 3.5 and 3.75 GB, and the installed system RAM does not violate this space.
The net result is that at least 3 GB of RAM should be fully accessible, while when 4 GB of RAM installed, ~700 MB of of the RAM is overlapping critical system functions, making it non-addressable by the system.

http://www.everymac.com/systems/app...ore-2-duo-3-gb-memory-limitation-details.html

 

[iThinkergoiMac]

Most likely that unavailable 256MB is the shared memory used for your graphics card.

Not possible. It's a MBP, and this is before the 13" and the days of 2 graphics cards. That model only has a discrete card, which has its own dedicated memory. On top of that, my MacBook has 6 GB RAM, and all 6 GB show up in the Activity Monitor, even though my GPU is stealing 144 MB RAM from the system.

 

[dyn]

64 bit booting IS default on the 2010 Mac Pro and will be default in many future Macs.

The new 2011 MBP's now boot the 64 bit kernel as well. If you want to boot the 32 bit kernel search for how to boot the 64 bit kernel and simply replace 64 with 32 (which is exactly what I did to make my MP boot the 32 bit kernel so I could use macfuse and apcupsd again).

 

[IceMacMac]

The new 2011 MBP's now boot the 64 bit kernel as well. If you want to boot the 32 bit kernel search for how to boot the 64 bit kernel and simply replace 64 with 32 (which is exactly what I did to make my MP boot the 32 bit kernel so I could use macfuse and apcupsd again).

Yes my mbPro 2011 has worked in 64 bit kernel mode since day 1. My desktop Mac on the other hand never was booted in that mode until last week. I've had to delete and update a lot of old junk in the digital closets.

I am comfortable switching back and forth between the boot modes and I'm by no means in a dire way. I'll sort it out. Actually I'm beginning to wonder if my Finder Freezes have been caused by something other than RAM or boot modes... Time will tell.