CompuServe Messages

Joe, EMM386 and QEMM386 allow 386/486 machines to use EXTENDED memory as EXPANDED memory. This requires the use of a page frame in the memory space between 640K and 1M. Expanded memory can be used by many programs such as Quattro to allow large amounts of data to be processed. AutoCad through release 9 used this method. The newer versions of AutoCad use extended memory directly using a DOS extender and don't require expanded memory. Both EMM386 and QEMM386 have an additional feature – they allow TSRs and device drivers to be loaded into the space between 640K and 1M. If EXPANDED memory is not required, a NOEMS switch can be set and the 64K page frame will also be available for TSRs and drivers. What I don't understand is why AutoCad, which doesn't use expanded memory, won't run correctly when NOEMS is set. I suspect that there is a memory conflict. When NOEMS is set, the TSRs and drivers load into a different physical address – probably within the page frame. When expanded memory is enabled, the page frame is not used when AutoCad runs so the conflict does not occur. Does this make sense? Ray