Why is the usable memory on my Macbook pro shown as 2.74 Gb when there is 4GB installed with 32bit Windows 7?

Possible Duplicate:
Windows XP and RAM 3.5GB+
Installed RAM : 4 GB but 2.96GB Usable......why?

I have a Macbook Pro with 4GB of installed RAM. I have installed Windows 7 on it which shows the usable memory as 2.74GB. Why is this? Don't tell me the 32 bit story; I program for a living. The maximum addressible memory on a 32 bit system is 4 GB not 3 GB.

Need proof? MSDN: Memory Limits for Windows Releases

bobbyalex

Posted 2011-03-02T17:51:00.753

Reputation: 443

3"Why isn't my top speed higher than 50mph when I tow my boat behind my VW Bug? Don't tell me the horsepower story; I drive a cab for a living." – Shinrai – 2011-03-02T20:42:27.767

Already beaten to death topic, Look at http://superuser.com/questions/50138 http://superuser.com/questions/27086/windows-xp-and-ram-3-5gb http://superuser.com/questions/7964/where-did-the-other-8-gb-of-ram-go http://superuser.com/questions/17827/using-3-gb-ram-in-vista-windows732-bit http://superuser.com/questions/54056/why-is-usable-ram-less-than-total-ram http://superuser.com/questions/27006/how-to-check-ram-size-without-looking-at-motherboard

– Sathyajith Bhat – 2011-03-03T06:16:14.197

Answers

Dont tell me the 32 bit story; I program for a living

It's the 32 bit story. Some things other than memory use the same address space, e.g. Memory mapped I/O.

Need proof?
http://en.wikipedia.org/wiki/3_GB_barrier

Snc

Posted 2011-03-02T17:51:00.753

Reputation: 101

2Not to mention video memory. – Matt Ball – 2011-03-02T18:27:43.373

1Definitely the 32 bit story. – Metril – 2011-03-02T18:48:03.510

2+1. Just because you're a programmer doesn't mean you know everything. Other devices get access to the 4GB address space FIRST, RAM gets whatever is left. Install 64-bit Windows and watch what happens. – Shinrai – 2011-03-02T20:21:38.563

The biggest user of memory is normally the video card. If it has lots of memory, that memory is lost, as described in : The usable memory may be less than the installed memory on Windows 7-based computers

You may examine the memory usage on the computer by opening the Device Manager and under the View menu, choose "Resources by connection". Expand the Memory node and see if you can figure out what, if anything, is occupying the memory. In some cases, memory can be increased by disabling unused devices such as firewire.

Note: The so-called 3GB barrier is more like 4GB before it is eaten up by the devices.

harrymc

Posted 2011-03-02T17:51:00.753

Reputation: 306 093