Hmmm. I can fully understand why there's only 264K free in the base machine (which has 512K RAM) -- memory is taken up by buffers, stack, the 'status' program, and so on. But to loose 12K of every 512K for I/O buffers seems a little odd. Or for extra page desriptors, or.... I could understnad if some memory was used ot record the fact that it had a memory expansion oard fitted, but 12K??? and why is it pro-rata for the amount of memory added? I assume thats saracsm. It's a very simple upgrade -- it was obvious what the extra chipos should be, it was also obvious what most of the links did. And I do have a 'factory' 1M board in my other Integral (although I could have worked it out without that). -tony