Is there a point to the 3gb switch if you have 2 gb of ram

Our CAD systems have 1.5 GB to 2.5 GB of RAM. When running without the 3 GB switch they usually start to behave badly when we get up to about 1.3 GB of memory used. With the 3GB switch, they usually are OK up to 1.6 GB or more.

Jerry Steiger Tripod Data Systems "take the garbage out, dear"

If you need more than 2 Gb total memory, you've little choice.

If you routinely operate at 1.5-2 Gig of useage, then enabling the switch and adding some ram ( provided your MB can take more ) will help to keep windows from using virtual memory.

If its uncommon to operate in that area then I'd not enable the switch as there are some known stability/compatibility issues (ie some software outright fails when more memory is installed than it was written to use). Gibbs cam 1999 will fail when more than 1 Gig of total memory is present ( that one took a looooong while to figure out ).

For some reason, windows likes to start using the swap file when there is about 30% of physical memory still available. This can considerably slow down your machine.

In either case, disabling virtual memory all together should show a performance inmprovement during borderline memory limitation sessions (from the physical ram speed, and R/W issues that are inherant to vm ) and have no adverse effects. Without the switch and having 2Gb installed, you are pretty much at the limit anyhow. With the switch and a bit of added ram, same thing. It would not be necessary without windows tendancy to unnecessary dip into virtual memory.

Yes, without the 3GB switch you will crash when your memory usage reaches about 1.6GB. With the switch you get about 1GB more before you crash. SW sometimes uses scratch files that grow and shrink while calculating. Even though you may be paging to disk that is preferable to crashing. So even with 1GB there is benefit. And if you go into "thrash" mode enough times you can use that to justify more RAM. Without the switch you will not know what is going on because you crash.

You can access all 3 parts of an article series on the 3Gb switch here.

Or if you can't get into there, you can also find it here. is a link into the articles directory of our SW User group site. I put a copy of several misc articles I have written or collected, so take a look at what else is there - you might find something else that tickles your fancy.

WT

Thanks for all your replies,

Wayne, I did read your articles (and Ed's) and found as you mentioned that xp failed to boot properly unless I added the userva=2900 switch you mentioned.

As was mentioned, if your running out of ram you have no choice, I couldn't print a pdf of a section view drawing from my assembly today without getting the "sw can't obtain ....... memory" message. And yes, this was happening in the 1.4 gb range as mentioned.

After the switch I was able to print just fine.

Zander

Do you have a lot of tasks running in the background?

For the record...

I have 2GB installed and am thinking of running the 3GB switch, but I've been working on one of my larger assemblies today using 1.75GB and no crashes.

It varies a lot. I've gotten up into the 1.6GB range without the switch as well, but "usually" start getting funny things to happen in the 1.3 to 1.6 GB range. I've also had SW behave oddly while using less than 1 GB even after the switch.

You could also have more stable systems or work in a more stable manner than we do. We seem to have more crashes than the average user. I think its because we have too many flaky in-context relations and too many flaky surfaces.

Jerry Steiger Tripod Data Systems "take the garbage out, dear"

Thanks, any test results with this one:

"/USERVA= This switch is only supported on Windows XP and Windows Server 2003. Like the /3GB switch, this switch gives applications a larger address space. Specify the amount in MB between 2048 and 3072. This switch has the same application requirements as the /3GB switch and requires that the /3GB switch be present. Applies to 32-bit systems only."