Make Windows XP (+Vista/Win7 32bit) access more RAM

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Fletch
Posts: 11711
Joined: Fri Mar 20, 2009 2:41 pm
OS: PC 64bit
SketchUp: 2016-2021
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Make Windows XP (+Vista/Win7 32bit) access more RAM

Post by Fletch » Thu Sep 30, 2010 12:27 pm

If you have Windows XP Pro and 4 Gb of ram, it's currently limited to only 2Gb. :| Yes, you may have 4Gb installed, but the programs only access 2Gb, no matter how many XP "Sees" that you have.

Let's not worry for now why this is, but there's a solution.
You can open up 1Gb more of RAM, and it's fairly easy to do.

Here are step-by-step instructions for getting more of your RAM available for SketchUp and Twilight Render.

If you have done this, please report back to us, and let us know and how it goes.
It must be understood that enabling the /3GB switch is for XP Pro, and can cause system instability depending on the system used, available RAM and Hard disk space, etc. Proceed with caution, and always with a backup.

btw Vista 32bit will not use /3GB boot switch, only XP. It's safe to enable.
Vista and Win7 32bit users should use this.

64bit systems should already allow 4Gb of RAM for 32bit programs... unfortunately this appears to be the max. allowable RAM for 32bit programs, so even if you have 12Gb of RAM, SketchUp (& Twilight) can only use 3 due to 32bit limitations.

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Fletch
Posts: 11711
Joined: Fri Mar 20, 2009 2:41 pm
OS: PC 64bit
SketchUp: 2016-2021
Contact:

Re: Make Windows XP (+Vista/Win7 32bit) access more RAM

Post by Fletch » Wed Jul 06, 2011 6:53 am

The following is from a short article provided by Twilight Render for SketchUcation's CatchUp Newsletter. As it describes the issue in more detail than the post above, it is provided here as a supplemental article.

Twilight Render was made Large Address Aware (LAA) with v. 1.4.5 in October 2010. Since then, SketchUp 8 has also became "LAA".

This could mean that Twilight and SketchUp have access to more RAM than a default system setup can give.

This is a confusing topic even for "geeks" but basically, if you have a 32 bit operating system and have 4GB of RAM in your machine, the 4th Gb of RAM is NEVER used by your programs. It's just sitting there, waiting for you to install a 64bit Operating System (OS).

In addition, 32 bit programs (applications or "apps") are only allowed access to 2Gb. So if you are rendering on a 32bit system or even with a 32 bit application on a 64 bit system, it may only be allowed to access 2Gb (not LAA) or possibly 4Gb (if LAA enabled). While a 64bit application on a 64 bit OS can access a LOT more RAM. (theoretically limited only by your motherboard capacity to hold RAM)

Now that SketchUp and Twilight are "LAA" the 32-bit applications can access up to 4Gb on x64 operating systems and up to 3 Gb on x86. 64-bit versions of Windows may* require no modifications to the operating system to benefit from LAA; however, in 32-bit versions of Windows, you must increase the user memory setting (/3Gb switch). It is not difficult to do, but it is a bit "geeky" involving a snippet of code in the boot.ini file. You do NOT want to do this, unless you have 4Gb of RAM installed on your 32 bit system. This is because it will limit your OS to only 1Gb and give the other 3Gb of RAM to your applications. The "catch" is that for many systems, even with 4Gb of RAM, enabling the switch causes the system to become unstable and possibly not boot at all. Or it can result in failing driver and service configurations. But for those adventurous types, the option is now available.

Keep in mind that there are 2 parts to the "LAA" equation if you have a 32 bit operating system. One must have both an application that is LAA, and command their 32 bit operating system to allow the application to use the additional Gb of RAM. A detailed tutorial on enabling the /3Gb switch in Windows XP PRO can be found here. Find a tutorial for enabling /3Gb switch for 32 bit versions of Vista and Windows 7 here. See also this Microsoft article.

* 32-bit applications on 64-bit platforms can address up to 2 GB, or up to 4 GB when an application is Large Address Aware.
* 64-bit systems provide 8 TB of virtual address for applications and 8 TB reserved for the kernel.

Please note that only skilled Administrators or personnel should attempt to perform the operation above. Twilight Render cannot be held responsible for any problems occurring with your system as a result of attempting to change the boot .ini file. As always, thorough research of the process and it's consequences is highly recommended before proceeding.

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