/3GB and xp64?

[Stilez]

I have some 32 bit software that uses close to 2 GB memory ("VM size" in task manager). There is no 64 bit version yet. The system is XP64 with 8 GB ram.

If it turns out the software is complied "IMAGE_FILE_LARGE_ADDRESS_AWARE" then can I set windows to load with the /3GB switch, allowing 32 bit programs to use more than 2 GB while not adversely affecting other 32 or 64 bit software or the OS itself?

Most discussion of /3GB is in the context of XP32, and most memory-demanding programs run a 64 bit version. So I haven't actually seen this question asked elsewhere.

What would the effect be on that program? On the system as a whole?

[cluberti]

If the image is aware, you don't have to do anything - on WOW64 it'll actually have access to all 4GB of VA (there's no kernel VA to share in WOW64). The x64 kernel doesn't handle it (like it would on boot on x86), and WOW64 has no configuration for /3GB because of the way it's designed, anything compiled LARGE_ADDRESS_AWARE will automatically have access to all 4GB of it's VA in it's WOW64 process.

[Stilez]

If the image is aware, you don't have to do anything - on WOW64 it'll actually have access to all 4GB of VA (there's no kernel VA to share in WOW64). The x64 kernel doesn't handle it (like it would on boot on x86), and WOW64 has no configuration for /3GB because of the way it's designed, anything compiled LARGE_ADDRESS_AWARE will automatically have access to all 4GB of it's VA in it's WOW64 process.

Thanks, helpful.