Running 32 bit VM on 64 bit Mac OS - is there 3GB memory limitation?

[LongGe]

Hi, All

I am considering switching to a MacBook Pro with 4GB ram installed. I am intending to run SAP stuff on Windows 2003 SQL Server using VMWare Fusion on the MBP. On a windows PC, there is an inherent limitation in that even though I have 4GB physical ram installed, only 3GB will be usable on a windows machine because of the inherent PC architecture (this is from IBM tech support). Can someone advise me if I will face the same issue if I run VMWare Fusion on the MBP ie is there still this 3GB of memory limitation even though I have 4GB of ram in my MBP?

Thanks in advance.

Message was edited by:

LongGe

[NeilBradley · Accepted solution]

Unfortunately I can confirm that this limitation exists due to the implementation of 32 bit XP.

[getwired]

If you need access to more RAM than that, you should be using an x64 version of Windows.

[aliasme]

Hey guys - do a search for:

Physical Address Extension

3GB PAE switch

This should solve your problem.

[LongGe]

Hi, All

Thanks for your replies. Can I confirm my understanding as follows:

If I want to use all the 4GB ram, I should be running the following virtual machine on my MBP:

\- VMWare Fusion (is this 64bit?)

\- Windows 2003 Server Standard 64 bit?

Thanks in advance.

[aliasme]

Whoops, yes, scratch my earlier suggestion. 4GB is the limit in 32-bit Windows XP.

Windows 2003 or Windows XP x64 Edition are what you need for more than 4GB of memory. Or technically Windows 2000 Datacenter editing on an IA32 chip can also support 8GB or so.

If you are running into memory problems right now, using the 3GB switch will give you another 1GB for your apps. Google it if helpful --- there are great Wikipedia entries on this.

[LongGe]

Hi, Aliasme

Thanks for your reply.

So, since the Macbook Pro can only go up to 4GB physical ram max, I can still use XP Pro 32 bit or Windows 2003 Server Std 32 bit as these 2 dont have that 3GB limitation?

I will check out that 3GB switch you mentioned.

[aliasme]

The switch is for XP 32-bit (and by proxy probably works on 2003 as well). It goes in the boot.ini and causes Windows, which normally allocates 2GB for the kernel and system, to limit that address space to 1GB, giving you 2GB+1GB for applications.

[LongGe]

Hi, Aliasme

Thanks !!

[SMB1]

If you install onto a macbook pro with 4GB and try to give your VM 4GB ram, you do know you'll be swapping a lot of that ram out right away killing your performance right?

[Harliv]

If you have 4GB of ram in the MBP it wouldn't be a good idea to use the full 4GB of memory allocated the Virtual Machine. This will cause the host system to swap and slow down. If you are trying to run the full 4 GB via Bootcamp then you should be ok as long as you are running less than that when you boot it under VMware.

[LongGe]

Hi, SMB and Harliv

Thanks for your post. Thats a good point. I hope that it does not mean that I am worse off than sticking to a Windows PC with 3GB ram!! What would your recommendation be on how to split that precious 4GB ram?

Message was edited by:

LongGe

[Harliv]

That really depends on how much you are running on the Host side when the VM is running. You should definitely be able to run 3GB. You likely can go beyond 3GB but not all the way to 4GB. The best thing to do is to start up what you expect to be running on the Host side and check your memory utilization. Its best to leave a little bit of room for overhead.

You can also run some experiments and adjust a little bit if needed.

[LongGe]

Hi, Harliv

Point noted. Thanks !