Windows 3 GB Switch

[Jeff Conrad]

I've seen quite a difference from the /3GB switch. The key to whether or not PS is broke is the amount of paging you're currently getting; if the available scratch is usually more than you're using, the switch won't help much. If the opposite is true, the benefit can be considerable, and the larger the file, the greater the benefit.

Windows memory allocation is described at http://msdn2.microsoft.com/en-gb/library/aa366778.aspx

The amount of available RAM varies with system configuration. The 4 GB address space includes memory-mapped hardware such as video RAM, so My Computer|Properties typically reports only 3 ~ 3.5 GB of available RAM. Depending on the reported RAM, you may need to allocate slightly less than 3 GB RAM to PS; this is easily accomplished with the /USERVA switch.

Though the explanation that follows may look intimidating, adding the switch(es) is simple; if all goes well, it takes about five minutes. Setting up a dual boot is a good idea. It's not that hard to fix a non-bootable system from the recovery console, but why chance the grief?

The boot switches are described at http://www.microsoft.com/technet/sysinternals/information/bootini.mspx

Putting the Switch in boot.ini

The easiest way to modify boot.ini is via

My Computer|Properties|Advanced|Startup and Recovery|Settings

which saves you the trouble of changing permissions on boot.ini so that it's writable.

Click Edit to open boot.ini with notepad, which is much easier than working in the list box. Depending on how your UI is configured (mine looks like the "classic" Windows 2000), you may need slightly different sequence to access the boot.ini dialog.

The default boot.ini usually looks something like

[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" /noexecute=optin /fastdetect

The safest approach is to copy the last line and paste it before or after the existing one, and then edit the first line under [operating systems] to look something like

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional 3GB" /noexecute=optin /fastdetect /3gb

Depending on how much RAM your system reports, you may need to give the system a bit more memory by also including the /USERVA switch, which allows you to specify between 2 GB and 3 GB for a user process. With this switch, boot.ini might look something like

[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 3GB" /noexecute=optin /fastdetect /3gb /userva=3000
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect

At boot, the [operating systems] choices will appear on the boot menu (much like the situation with different OSs). The quoted text following WINDOWS= is what appears in the boot choices when you have more than one entry; the only reason for changing the text for the first entry is so that you know which one you are choosing. It's probably worth having two entries in boot.ini, at least initially, so that you can boot the default if the new entry doesn't work.

Note that the /USERVA switch takes an argument in MB, and, for reasons known only to Microsoft, requires that the /3GB switch also be given. My computer (with 4 GB RAM), reports 3.25 GB, and I currently specify /USERVA=3000. PS shows about 2.56 GB available, and I'm currently giving it 100% of that. I've not done any systematic testing to see if these are the best values.

Don't change any other lines in boot.ini; save the file and quit notepad. You may wish to change the 'Time to display operating systems:' from the default value of 30 seconds so that you don't need to manually select the new OS choice to avoid a 30-second delay before it boots by default (I found that 15 seconds was more than enough). After you confirm that the new configuration boots and works successfully, you may want to delete the original entry to avoid any delay at boot. I've done this and have not had any problems so far.

You may also need to check the size of the paging file, via

My Computer|Properties|Advanced|Performance|Settings|Advanced|Virtual Memory|Change

[Mark Stahlke]

There is a caveat to giving Photoshop most of the available memory in a Windows system: printing.

Photoshop CS2 doesn't use its own memory for print spooling. It uses the system's memory. If you allocate something like 75% of the memory to Photoshop, do enough work on a high resolution file that Photoshop has consumed most of its memory allocation, and then attempt to print the file from Photoshop, your print may be truncated because there is not enough system memory available to spool the entire print job.

At one time I was ready to throw my printer out the window because I thought this was a driver problem. Eventually I found that reducing Photoshop's memory allocation gave me more of the print. Today I give Photoshop about 25-30% of the memory and I can print reliably. By the way, this is a 4GB machine.

Oh yes, then there's scanning. I've had a similar problem trying to scan from Photoshop using the TWAIN driver - not enough memory for high resolution scans. Now I always scan outside Photoshop and then start Photoshop and open the file.

NOTE: This issue exists with Photoshop CS2 running on Windows 2000. It may or may not exist with other versions of Photoshop or other versions of Windows.

Cheers,
Mark

[Joanna Carter]

Be aware that, even with the 3GB switch, a great many motherbards, especially those over a year old, will only use 2.5GB, due to misplacement of the memory allocation for the PCIExpress system. Some motherboard manufacturers have issued firmware updates, some haven't.