Max memory addressable

I just ordered 4x 1gig sticks for my new built Windows 2003 Server machine (32-bit), Core 2 duo.

I read online that 32-bit OSes cannot address the whole 4 gigs of ram..max was like 3.2gigs. Is this true? Will the other 800mb of RAM be discarded??? This is a server os...

I am running a Windows 2003 Server with 4GB of ram. It sees and can use all of the 4 GB. It is Windows Server 2003 Standard (32 bit). Should work fine.

manbush said:

I just ordered 4x 1gig sticks for my new built Windows 2003 Server machine (32-bit), Core 2 duo.

I read online that 32-bit OSes cannot address the whole 4 gigs of ram..max was like 3.2gigs. Is this true? Will the other 800mb of RAM be discarded??? This is a server os...

Click to expand...

Isn't that sort of a hack??
Anytype of 32-bit OS can only access 3.2 gigs DIRECTLY. They can however access the full 4 gigs using PHYSICAL ADDRESS EXTENSIONS. If you go into your "properties" of "my computer", you can see "Physical Address Extension enabled". That is a hack.

On a 64-bit OS, you don't see that..that's because it can address over 4 gigs.

Am I right? (I'm no expert).

What edition are you running? 03' Web is good for 2gb, 03' Datacenter edition is good for 128gb for x86 and 2TB for 64-bit. (This is just OS max, hardware needs to also support the amount of ram you want to run)

Check it:
http://www.microsoft.com/windowsserver2003/evaluation/sysreqs/default.mspx

I'm running Windows 2003 Enterprise Edition SP1.

Although Microsoft says it will access 4 gigs on a 32-bit OS...it really can't. It's using a hardware hack called PAE (physical address extension).This hack is used only in 32-bit OS if you have more than 3.2gigs of ram. In 64 bit, it does not appear.

Look at your computer properties..under total ram, it will say if physical address is enabled or not. This also means that NO single app can have more than 2 gigs of RAM at a time if they are not COMPILED with a special switch/flag (/LARGEAWAREADDRESS).

In 64 bit, it has TRUE support for over 4 gigs. No hacks needed.

Then you should be good up to 32gb, which means you're only limited by your motherboard's max memory.

Bios24 said:

Then you should be good up to 32gb, which means you're only limited by your motherboard's max memory.

Click to expand...

Yes BUT it's 32-bit....and BECAUSE it's 32-bit IT WILL use a HACK.

A HACK. A HACK called Physical Address Extensions. I will test this theory out when I get home by writing a program.

The program will declare a long variable and increment it in a loop by 1000000 each time while I monitor the RAM usage. It should go upto 4 gigs (4000mb) leaving the system with 24mb. When it reaches 4 gigs, it will crash. Windows will NOT page it because it's a concurrent process.
If this works, it will prove wheather Windows can really address 4 gigs of RAM (a single app can reach it etc)

I dont have PAE enabled, and my server sees and will use the entire 4GB. I have maxxed it out a few times.

bchur83 said:

I dont have PAE enabled, and my server sees and will use the entire 4GB. I have maxxed it out a few times.

Click to expand...

I have Windows 2003 32-bit Enterprise and I see PAE is enabled.
If I go into safe mode, I only see 3.5gigs of RAM...which implies that PAE is a hack. Infact, if you examine boot.ini, you can now see it has a /pae flag enabled (or something of that sort).

Windows 2003 64-bit however does not need PAE.

Another note is that PAE requires a 36bit memory register or higher. PAE uses the last four bits to keep setup four 32 bit registers. Performance in some cases can be hurt because of this setup and all of the continuity checks involved. Its not really a "hack" but just a way to utilize a function of Intel CPUs (to my knowledge no 32bit AMD CPU can use PAE).

Technically speaking a non-64bit CPU could very well use over 4GB without PAE. It's all dependent on the memory register width (32bit on most non 64bit CPUs, 36bit on many late model 32bit Intel CPUs, and 48bits on 64bit x86 CPUs). PAE was just a way to put off rewriting the kernel. I believe Linux also has a similar setup.