/3GB switch - how to enable it

Thanks to a bunch of folks contributing to a thread on PWx running out of
memeory, I've learned the following:
1. No matter how much memory you have, or how big your virtual memory,
Windows will not allow you to use more than 2GB for a single application.
On top of that, the 2GB is theoretical - in practice, applications will
crash when memory usage gets to about 1.6-1.7 GB. This of course will stop
you cold if you are working on large assemblies or on PWx renderings.
2. Because of the 32-bit operating system, the mathematical limit for total
memory+virtual memory is 4GB. By defualt, Windows reserves half of that
total for itself (greedy bastard of a program)
3. Windows XP Pro and some server applications have whats called the 3GB
switch. It is not like a little button that you press to turn on, though.
One has to hack their boot.ini file in order to enable it. The following
article seems to describe what to do:
formatting link
when I change my boot.ini file to add /3GB as shown in the
sample, my system will not reboot and I have to go to a backup of my hard
drive to recover and change my boot.ini to its backup.
So my question now is:
I have reviewed many threads on this subject on this newsgroup, but none
that I saw go into any real detail on how to make it so. For all of you
large asssembly folks, or anyone whose crashed because of lack of memory,
this seems like it would be pretty generally useful. So I am making this
broadcast appeal:
A) Has anyone actually enabled their /3GB switch?
B) Can you please post the contents of your successful boot.ini file so we
can see the proper syntax?
C) Does its implementation depend on processors, motherboard, or anything
like that? Even if you do it right, can it fail because of some other
Reply to
Edward T Eaton
Loading thread data ...
Are you running 2004. Do you know if they fixed that memory leak in PW2. I know that that made my computer crap out. It seemed to go away if you had fully resolved all light weight components. I didn't see any reference to this in the other post.
Reply to
Corey Scheich
Yup, the memory leak seems to be gone in 2004 (thank god). We just have to maneuver to stay under a total of 1.6Gig of memory usage, unless the /3GB switch can be enabled AND PWx can take advantage it like SWx is supposed to..
Reply to
Edward T Eaton
i don't have enough memory. but ... i believe you really need >3gb for this to really work (3gb for sw & something left for OS and remaining processes)
[operating systems] multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /3GB /fastdetect
failure is possible, xp pro sp1 may not start. if you search for "/3gb switch" on support.micorsoft.com, this issue should be listed 1st in the search results
in addition to searching for /3gb, try searching for "4gt ram tuning" on microsoft. btw, some of the original information on this subject i can no longer find.
Reply to
kenneth b
I just got what I think is a complete story from a guy at our VAR, CATI (thanks!); they had already slogged through this issue a month or so ago, and had the answers. Kenneth b has posted a lot of the same information (thanks, too!).
Bottom line - Windows XP Pro, Service pack 1, the /3GB switch is simply broken. It doesnt' work, and there might be no plans inplace right now to fix it. In Windows XP Pro, service pack 0, the performance of the /3GB switch was spotty at best. The failure to reboot that I encountered is typical of what happens when someone tries to turn on the 3GB switch.
SolidWorks' mention of the 3GB switch on page 7-12 of the 'whats new' manual for 2004 is just them doing their job. SolidWorks is written to take advantage of it, if it works. The thing that everyone neglects to mention to saps like me is that it doesn't work.
So, save your money if you are on Windows XP Pro - don't buy any more than 2GB ram, because SW can't touch it (or can't touch it reliably if you are on SP0 of Windows). At least that's according to the information I have. -Ed
Reply to
Edward T Eaton
btw, you could always go back to w2k, i believe it (/3gb) works ok with sp2 or greater
Reply to
kenneth b
I wonder if Microsoft Windows Small Business Server 2003, Standard Edition is any better? Ususally, the server version of Windows does the switch without any problems.
I'm also wondering if the 64bit OS from Microsoft is in beta yet ;^)
Mike Wilson
Reply to
Mike J. Wilson
This is the last I heard about that:
formatting link
Reply to
Dale Dunn
Yes, Windows XP Professional, SP1 is broken and can not utilize the 3GB switch. But there is a patch! And with the patch, everything works as advertised - plus, PWx-2, SWx2004 can use the extra memory for renderings.
To get the hotfix, you have to call (800) 936-4900 and get to the 'hotfix' people. Don't get spooked by Microsoft's statement that they will charge $245 for tech support - hotfixes are free.
Let the person on the phone know the problem has to do with the 3GB switch, referred to in article 328269. The link for that article is
formatting link
Microsoft will email you a hotfix that carries no warranty and is not recommended for use in a production setting unless you thoroughly test it. But, for the record, it works. I just did a rendering that always killed my machine due to lack of memory, and now it completes.
WARNING: Yes, this has worked for me, but I have no idea yet if it will mess something else up. I was just in a bind and had nothing much to lose - plus, I have a complete backup of my boot drive than I can plug in and roll with if this goes south.
By the way, kenneth b was 100% correct. The syntax for modifying your boot.ini is: multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /3GB /fastdetect
To get to your boot.ini file, you have to either a)go to wndows explorer>tools>folder options>view and remove the checkmark next to Hide protected operating system files. This will allow you to see your boot.ini file on the root level of your C: drive.
Or - you can RMB my computer>properties>startup and recovery. Click 'settings' then click 'edit' in the next window that pops up. Now you can hack your boot.ini file - BUT ONLY DO IT AFTER YOU HAVE ENTERED THE PATCH AND BACKED UP EVERYTHING.
Reply to
Edward T Eaton
Thanks for posting that Dale. I may look into getting my hands on a copy of that. I plan on creating a new system soon with the possibility of using the 64 bit Athlon.
Here is a 64bit WindowsXP system you can buy now if you have the bucks...
formatting link
I like their sales pitch... "If you are constrained by memory limits or you need the exceptional price performance of these 64-bit parallel performing workstations then look no further. Our Itanium 2-based workstations have all the power you need at affordable prices".
Mike Wilson
Reply to
Mike J. Wilson
I doubt SW would run on an Itanium because they don't to my knowledge have a 32bit compatibility mode like the Hammer does.
Reply to
Yeah, I remember hearing something about that. Intel has a different strategy than AMD regarding compatibility. So if SolidWorks doesn't decide to recompile their software, we may be forced to use AMD if Intel dropped 32bit chip manufacturing (an extreme scenario of course).
Reply to
Mike J. Wilson
Have you tried restoring an XP system image yet ? I've heard that it won't work. The gist was, there are some system files XP will not allow to be copied. Part of their wonderful new security BS
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Reply to
That isn't so bad. You make it sound like having to take Castor Oil. :)
They were running SW on a Hammer at the last SWW.
I'll just bet there are a few people at SW who would like to port the software to some of these platforms. AMD has put Intel in a pickle because they can run off the shelf apps like excel and word while I don't think Itanium can. I think the AMD will hit the enthusiast and power user market well before the IM. And SW goes where the market goes.
Mike J. Wils>> "kellnerp" wrote...
Reply to
You must come from white-box land. HPs prices are very good. Ever get a quote for a Silicon Graphics?
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