## Display Device Driver Reference for OS/2

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### The Phunk

When the XGA driver has to perform a BitBlt from system memory to VRAM, it copies up to 64KB of the source into the Phunk, and then completes a BitBlt from the Phunk to the screen by way of a bus-master. The 8514/A does not have the ability to process bus-master transfers. The 8514/A driver still uses the Phunk, however. For the 8514/A driver, the Phunk is a 64KB memory buffer that is not locked down. The 8514/A driver copies up to 64KB of source data into the Phunk, by way of eddf_MESS(), and then copies from the Phunk to VRAM by way of software through the 8514/A pel port. For the 8514 /A, the major impact of this process on the low-level routines of the driver is that these routines have to deal with a source or destination that is system memory; whereas the XGA low-level routines do not. (Refer to BitBlt, which describes the uses of the Phunk in more detail.)