How to use AGP memory

I have a geforce3 with 64Mb RAM and I use the openGL extension called glvertexarrayrange. With this extension i’m supposed to be able to use AGP memory with the command “wglAllocateMemory”.
I’m able to use my video card memory by using the values 0 , 0 , 1 for the parameters “read”,“write”,“priority”. I’ve tried the values 0 , 0 , 0.75 to use the AGP memory, but the command return the null pointer. Haven’t I enough AGP memory ? Can I change this ? How ?


check these things to determine the problem:

  1. Is AGP enabled at all? Sometimes the drivers won’t work with your chipset drivers and you end up running the card in PCI mode.

  2. Are you using a buggy driver set? I’ve seen a few OpenGL drivers wrongly thinking AGP wasn’t usable when it in fact was.

  3. Play more with the parameters. The Nvidia specs doesn’t say very much about the parameters, but the priority parameter seems to be the one to play with.

Good luck!

On Windows:

Right-click desktop; choose “Properties”.

Click the “Settings” tab, and the advanced button at the bottom.

Click the GeForce tab. It will have, towards the top of the window, a field saying “Bus type:”. If it says AGP (PCI Mode) or just PCI on that line, you don’t have correct AGP drivers installed for your motherboard.

To get the right drivers, go to the web site of your motherboard or chip set manufacturer, and download new drivers, and follow their instructions for installation.

i think read, write never have to be set both to 0; this is not a correct value.
However, this may not be your problem, but until your priorities are not null, read & write are intended not to be used at all.