Dual-boot, 4GB seen under Vista, wish to enable /3GB switch under

Have a dual-boot PC with Vista 64bit and XP Pro 32 bit.

I have enabled the memory remap in the BIOS so I now can see the 4GB (just
added another 2 GB on PC with already 2GB). In XP I only see 2GB (instead of
2.93GB when Memory remap was *disabled* - then Vista was just showing 2.93
GB...)

My understanding is that I should add the /3GB switch in the Boot.ini file
of XP, but I am unsure on how to do since I do not get the same look and
content : Microsoft suggest that the Boot.ini file should look like this then
add the /3GB at the end:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINNT="????" /3GB

But my Boot.ini file looks like this (pls note the *FASTDETECT
/NOEXECUTE=OPTIN* at the end :

;
;Warning: Boot.ini is used on Windows XP and earlier operating systems.
;Warning: Use BCDEDIT.exe to modify Windows Vista boot options.
;
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP
Professional" /FASTDETECT /NOEXECUTE=OPTIN


Do I simply add another space at the end and type ''/3GB'' (without the
quotes) ? Or shoud I remove anything before ?

Please remember that this is a dual-boot machine - I do not wish to screw
anything (as I am not expert enough to feel at ease to recover from such a
mistake...)

Thanks,
Rob

Ian
Mon May 26 08:42:53 PDT 2008


"Rob" <landrobert@gmail.com> wrote in message
news:EF314C16-A1D2-4DB9-91C6-238F848AC1DD@microsoft.com...
> Have a dual-boot PC with Vista 64bit and XP Pro 32 bit.
>
> I have enabled the memory remap in the BIOS so I now can see the 4GB (just
> added another 2 GB on PC with already 2GB). In XP I only see 2GB (instead
> of
> 2.93GB when Memory remap was *disabled* - then Vista was just showing 2.93
> GB...)
>
> My understanding is that I should add the /3GB switch in the Boot.ini file
> of XP, but I am unsure on how to do since I do not get the same look and
> content : Microsoft suggest that the Boot.ini file should look like this
> then
> add the /3GB at the end:
>
> [boot loader]
> timeout=30
> default=multi(0)disk(0)rdisk(0)partition(2)\WINNT
> [operating systems]
> multi(0)disk(0)rdisk(0)partition(2)\WINNT="????" /3GB
>
> But my Boot.ini file looks like this (pls note the *FASTDETECT
> /NOEXECUTE=OPTIN* at the end :
>
> ;
> ;Warning: Boot.ini is used on Windows XP and earlier operating systems.
> ;Warning: Use BCDEDIT.exe to modify Windows Vista boot options.
> ;
> [boot loader]
> timeout=30
> default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
> [operating systems]
> multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP
> Professional" /FASTDETECT /NOEXECUTE=OPTIN
>
>
> Do I simply add another space at the end and type ''/3GB'' (without the
> quotes) ? Or shoud I remove anything before ?
>
> Please remember that this is a dual-boot machine - I do not wish to screw
> anything (as I am not expert enough to feel at ease to recover from such a
> mistake...)
>
> Thanks,
> Rob
>
One question to consider is whether or not you want Vista 64 to work to
its full potential and have access to all 4 GB. If you do, then enable
the Memory Remap in BIOS and live with 2 GB for XP. That's what I
plan to do since XP works very well with 2 GB, and I increased it to
4 GB for 64 bit Vista.

If you prefer to work with Memory Remap disabled, you should add
/userva=2500 after /3GB in your boot.ini boot line. The reason for this
is to reserve enough memory for XP itself. The 2.93 GB you see is
reserved for applications, leaving little for XP itself, which has to share
its 1 GB with the hardware addressing, and may start paging to disk
and slow down. The /userva=2500 is a start and you may be able to
increase it to 2600 or 2700.

The /userva=xxxx switch is explained here:
http://support.microsoft.com/kb/316739

Jerry
Mon May 26 14:16:08 PDT 2008

A Google search on BOOT.INI will result in many comments about possible
modifications to the file itself.

"Rob" <landrobert@gmail.com> wrote in message
news:EF314C16-A1D2-4DB9-91C6-238F848AC1DD@microsoft.com...
> Have a dual-boot PC with Vista 64bit and XP Pro 32 bit.
>
> I have enabled the memory remap in the BIOS so I now can see the 4GB (just
> added another 2 GB on PC with already 2GB). In XP I only see 2GB (instead
> of
> 2.93GB when Memory remap was *disabled* - then Vista was just showing 2.93
> GB...)
>
> My understanding is that I should add the /3GB switch in the Boot.ini file
> of XP, but I am unsure on how to do since I do not get the same look and
> content : Microsoft suggest that the Boot.ini file should look like this
> then
> add the /3GB at the end:
>
> [boot loader]
> timeout=30
> default=multi(0)disk(0)rdisk(0)partition(2)\WINNT
> [operating systems]
> multi(0)disk(0)rdisk(0)partition(2)\WINNT="????" /3GB
>
> But my Boot.ini file looks like this (pls note the *FASTDETECT
> /NOEXECUTE=OPTIN* at the end :
>
> ;
> ;Warning: Boot.ini is used on Windows XP and earlier operating systems.
> ;Warning: Use BCDEDIT.exe to modify Windows Vista boot options.
> ;
> [boot loader]
> timeout=30
> default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
> [operating systems]
> multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP
> Professional" /FASTDETECT /NOEXECUTE=OPTIN
>
>
> Do I simply add another space at the end and type ''/3GB'' (without the
> quotes) ? Or shoud I remove anything before ?
>
> Please remember that this is a dual-boot machine - I do not wish to screw
> anything (as I am not expert enough to feel at ease to recover from such a
> mistake...)
>
> Thanks,
> Rob
>