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Journeyman III

Increase VM limit causes disabling of DirectX

Customer Support Directed Me To This Forum.

We have purchased 3 Panasonic Tough-Books (ruggedized notebooks) • CF-52E has a ATI Radeon™ HD 3650, 512MB dedicated VRAM • CF-52M has a Radeon HD 5650; Video Memory: 512 MB VRAM • CF-52S had the AMD Radeon HD 6750M. We use the boot.ini file to bump up the virtual memory usage limit to 2.3 GB via the switch “/3GB /userva=2300” on all 3 units. The video cards used in the 52E and 52M models worked fine with this boot.ini setting. However, the CF-52S’s with the Radeon 6750M video card disables DirectX when the command to bump up the VM is applied. Is this a known issue? Is there an updated video driver that can correct this or perhaps some switch setting? I've contacted Panasonic and they claim that the base driver provided by AMD was used without changes. 

I have also discovered the same issue with another ATI card.  The 2nd system that I am observing the same behavior on is a Dell using a AMD Firepro V4900 w/ chip type ATI Firepro V (FireGL V) w/ 1 GB VRAM.

The machines have 4 GB physical RAM and plenty of disk space.

Thanks for the help in advance,

1 Reply


the problem with the 3GB switch is that you reduce the memory that remains available for the device drivers. Usually 2GB can be used, when you set the 3GB switch the amount is reduced to 1GB. This space is shared by all drivers on the system. Depending on the devices in a system it might work well one one but fail on another system. I suppose when you see that DirectX fails due to this switch it is becaus the base driver runs out of memory. Actually there is not much you can do about it except trying some different values for userva or not using the 3GB switch. The amount of physical memory or available disk space has no influence since you only have 4GB of addressable memory.