The following options are of particular interest to the Oak driver. Each
of them must be specified in the 'svga' driver section of the
XF86Config file, within the Screen subsections to which they are
applicable (you can enable options for all depths by specifying them in the
Device section).
This option enables a linear framebuffer at 0xE00000 (14Mb) for
cards recognized as ISA by the probe. Cards that are VLB will
map the framebuffer at 0x4E00000. The aperture depends
on the VideoRam parameter in the XF86Config file or on
the probed value for the board. It will speed up performance by
about 15% on a VLB-based boards for a DX2-66 486.
This option will cause the command FIFO threshold of the chipset to be set at 2 instructions, which should be optimal for 16-bit data transfers, as empirical use of different thresholds with xbench show. Expect a 5-10% of performance boost on a DX2-66 486.
This option will set the FIFO to a safe value of 14, slowing the board by a 50%, use this only if you experience streaks or anomalies on the screen.
This option will enable an internal cache on the board that will be used as a rudimentary bitblt engine. Performance boost is more or less 100%, (double BlitStones on xbench). Most OTI087 boards seem to have this feature broken, corrupting text from xterms and leaving mouse droppings throughout the screen. As a rule of thumb, enable it, if it works badly, disable it ;).
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