4. Current implementation of generic VGA support for non-ATI adapters

Support for generic VGA with non-ATI adapters is also implemented, but has undergone only limited testing. The driver will intentionally disallow the use of this support with ATI adapters. This support must be explicitly requested through an xorg.conf ChipSet specification. This prevents the current VGA generic driver from being disabled.

This driver's generic VGA support is intended as an extension of that provided by the current generic driver. Specifically, within the architectural bounds defined by IBM's VGA standard, this driver will allow the use of any 256-colour mode, and any dot clock frequencies both of which allow for many more mode possibilities.

The driver will enforce the following limitations derived from IBM's original VGA implementation:

• There can only be a set of four (non-programmable) clocks to choose from.
• Video memory is limited to 256kB in monochrome and 16-colour modes.
• Video memory is limited to 64kB in 256-colour modes.
• Interlaced modes are not available.
• Colour depths higher than 8 are not available.