Is there any limit for VISA allocate DMA memory ?

[YuYiming]

Hi,

I have get an error: -1073807300, when I allocate memory for DMA larger than 4M Bytes.

Is there any limit for allocate memory for DMA ?

I have run the attach vi on win7 32bit or 64bit, It seems there is a limit at about 4M Bytes.

However I can allocate memory more than 20M Bytes on WinXP system. 

Is there any solution for win7 to allocate memory more than 4M Bytes ?

[James.M]

I'm running Windows 7 64bit and it errors out at around 6M. It's a little bit dynamic because sometimes it will work with 7M, but mostly only with 6M.

It's strange to me that there isn't more documentation around this. I can't find anything specific to the memory limit here, or even a general guideline. Hopefully someone else on here can shed some light.

[YuYiming]

The limit will change after you run this vi many times. On my computer, it change to 2M Bytes, 1M Bytes then 256k Bytes. After that , I restart LabView, the limits may go back to 4M Bytes. And some times, I need to restart computer. Is this vi have any risk for memory leakage ?

[James.M]

I altered the VI to loop from 1M in increments of 1M until it errored (as fast as it could) and then output the farthest it got without an error. Here is what the plot of those highest allocations looks like and attached is the VI.

[YuYiming]

Thank you for your help to test the vi. However I still want to know is there any limit for VISA allocate DMA memory. Or if I want to allocate a VISA memory more than 10M Byte, what shall I do ?

[natasftw]

Well, when you set it above a certain value it errors.  That sounds a lot like a limit.

He gave you a test so you could estimate where the limit is with your system.

[James.M]

I agree this isn't really an answer, especially because my test isn't really difinitive. I do hope that someone who knows the backend stops by and can give more info.

It seems like there's a relatively stable limit, but I don't know enough about VISA memory allocation to prove it.