## Display Device Driver Reference for OS/2

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### 8514/A Device Description

The majority of the I/O ports are either read-only or write-only.

There is a multi-function register that requires special considerations because the functionality characteristics are totally different from the other I/O registers.

The 8514/A internal RGB index of the DAC is not readable.

The VRAM cannot be accessed directly. (It is not a dumb frame device.)

Special consideration must be given to handling the passthrough-mode capability of this device.

Video memory size is assumed to be 1MB for the following reasons:

-The OS/2 PM Display Device Driver cannot function without it.

-It is not possible to configure a system with multiple 8514/A adapters.

The 8514/A is not a Direct Memory Access (DMA) device.