After some investigations, there is no known issue with this type of configuration.
The transfer rate seems to be low because this hardware is capable of upper data transfers.
Another think, what do you mean by "That is strange is if i click continously with the computer mouse, the transfert rate raise.", do I understand that's you are using the mouse in another program or you are coercing something your application.
I know it's very strange,
We record the data directly on an VXI harddisk, and after that software ask if we want to copy the data of the local bus (vxi hd) on the computer. We accept and an transfert window appears.
During the data download the transfert rate decrease continuisly until very low rate. If we click on the screen the transfert rate raise. We have inform the Dataphysics company about that and they not believe us. So we have made a short film showing that strange phenomena.
We have note one thing, when we click during the tranfert rate the green led of the VXI SCSI HD wink ...