## Display Device Driver Reference for OS/2

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### 8514/A Design Tradeoffs

When save/restore of the complete video state is required, you have two choices for saving the 1MB VRAM:

-Allocate the 1MB shadow buffer during creation of the virtual DOS session, thus eliminating a potential problem with resource allocation during session switching.

-Delay allocation of the shadow buffer at the time of session switch, but risk the possibility of session termination because the required memory is not available.

Software emulation of any hardware-assist operations to the video memory probably is too complex to achieve successfully. The only alternative available is to freeze the DOS application whenever these I/O ports are accessed in the background. A frozen image can be presented in a window if the complete video state and VRAM were saved for the DOS window session.