Intel845 IGP and XGetImage

[Austin Yuan]

   I am working on a project that transfers x window desktop from one
machine to another machine on intel845 platform. The transfer includes
3 operations: get the desktop image, pass it on network, and show the
image on another side. I use XGetImage/XPutImage to get and show the
image. Now the problem is that XGetImage takes more time than
XPutImage and becomes the bottleneck of the whole system(My simple
demo shows one XGetImage call takes 116498us,but XPutImage only
7362us). I trace XGetImage implementation on the server side. It will
fall into XAAGetImage, and because intel845 IGP driver doesn't
implement ReadPixmap(I think it is bitblt from framebuffer to system
memory), It will fall back to software bitblt.
   My question is whether intel845 IGP supports bitblt from
framebuffer to system memory. If not, why does XGetImage takes more
time than XPutImage,and how to optimize it?

Thanks!
Austin Yuan.