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phrozted · Nov 12, 2007, 07:24 PM

I just bought a Macbook with 4GB of memory. Installed Vista, and Vista under System Properties says that the computer is only running with 3,038 MB (3GB) of memory.

I just saw another post on this site by a guy who was having a similar problem with his Pro and Windows XP--in his case, Windows XP was showing that he only had 2GB of memory when he really had 3GB.

What's the situation here?

mduell · Nov 12, 2007, 07:48 PM

TabBlogger : The 3GB-not-4GB RAM problem

32-bit Vista supports up to 3.5GB RAM, although the actual amount depends on the chipset and can be as low as 2.75GB.

The 2GB-not-3GB problem is different, your friend just needed to use the /3GB switch.

phrozted · Nov 12, 2007, 07:50 PM

So do I need to buy a more expensive version of Windows?

mduell · Nov 12, 2007, 07:51 PM

I don't think the 64-bit edition is any more expensive than the 32-bit edition. Drop the $95 on 64-bit Vista if you really need that last gig.

MacosNerd · Nov 13, 2007, 06:13 AM

The issue with 64bit windows is that you'll need fully blessed,i.e., signed drivers. To my knowledge Apple has not released any and so you'll have to search the net for them (they're out there). 64bit vista unlike 32bit vista does not just give you an error for an unsigned driver it will refuse to load it. Then I heard some games have issues with 64bit windows. Not sure about that problem, just "word on the street"

By going the 64bit route for windows you're only gaining yourself access to more ram, but in exchange you have driver issues and some game compatibility

64stang06 · Nov 15, 2007, 10:47 AM

Originally Posted by MacosNerd

The issue with 64bit windows is that you'll need fully blessed,i.e., signed drivers. To my knowledge Apple has not released any and so you'll have to search the net for them (they're out there). 64bit vista unlike 32bit vista does not just give you an error for an unsigned driver it will refuse to load it. Then I heard some games have issues with 64bit windows. Not sure about that problem, just "word on the street"

By going the 64bit route for windows you're only gaining yourself access to more ram, but in exchange you have driver issues and some game compatibility

I'm glad I read that, I was about to upgrade my 32-bit Home Premium to the 64-bit but will wait. I don't do too much with Windows but play a few games and test web sites and such.

Tomchu · Nov 15, 2007, 11:25 AM

Any OS running in a 32-bit environment will hit this limit. Think of it this way ...

There are only 2^32 addresses available to share between RAM and devices (devices need addresses too). If you used all of those addresses for addressing RAM, you'd have access to all 4 GB of it -- but then you'd have no access to any devices, and that just wouldn't work. Depending on the chipset and amount of devices you have, 512 to 1280 MB of your address space will be used for devices. In your case it's about 1058 MB.

OS X will do the same thing when running in 32-bit mode (I think) -- unless it uses PAE, but that's a hack.

mduell · Nov 15, 2007, 05:53 PM

Originally Posted by MacosNerd

The issue with 64bit windows is that you'll need fully blessed,i.e., signed drivers. To my knowledge Apple has not released any and so you'll have to search the net for them (they're out there). 64bit vista unlike 32bit vista does not just give you an error for an unsigned driver it will refuse to load it.

Nice FUD there... requiring signed drivers is an option on 64-bit vista which is defaulted to on. You can disable it with bcdedit /set loadoptions DDISABLE_INTEGRITY_CHECKS from an elevated (admin) command prompt.