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<A HREF="Oak.html"><EM>Information for Oak Technologies Inc. Chipset Users</EM></A>
 <b>:</b> <EM>XF86Config options </EM><BR>
<b>Previous:</b> <A HREF="Oak1.html"><EM>Supported chipsets </EM></A><BR>
<b>Next:</b> <A HREF="Oak3.html"><EM>Mode issues </EM></A>


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  <H2><A NAME="2"></A>2. XF86Config options </H2>

<p>The following options are of particular interest to the Oak driver. Each
of them must be specified in the 'svga' driver section of the
<code>XF86Config</code> file, within the Screen subsections to which they
are
applicable (you can enable options for all depths by specifying them in
the
Device section).</p>
<p>
<dl>
<dt><b>Option "linear" (OTI087)</b><dd><p>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 <code>XF86Config</code> 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.</p>

<p>Sometimes a motherboard will not be able to map at 0x4E00000,
and then linear mode will not work with more than 14 Mbytes of
main RAM. I know this because mine doesn't.</p>
<dt><b>Option "fifo_aggressive" (OTI087)</b><dd><p>This option will cause the command FIFO threshold of the
chipset to be set at 0 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.</p>
<dt><b>Option "fifo_conservative" (OTI087)</b><dd><p>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.</p>
<dt><b>Option "enable_bitblt" (OTI087)</b><dd><p>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.</p>
<dt><b>Option "clock_50" (OTI087)</b><dd><p>This one will force the internal speed to 50 Mhz.</p>
<dt><b>Option "clock_66" (OTI087)</b><dd><p>This one will force the internal speed to 66 Mhz, speeding up
performance of the chipset.</p>

<dt><b>Option "no_wait" (OTI087)</b><dd><p>Sets the VLB interface to no wait states. On a medium VLB
board (mine is VLB/PCI, so its not a very fast one) in VLB
transparent mode, it manages up to 16 Mbytes/second transfer
rate through the bus.</p>
<dt><b>Option "first_wait" (OTI087)</b><dd><p>Makes the VLB interface to add one wait state to the first
read or write of a given burst.</p>
<dt><b>Option "first_wwait" (OTI087)</b><dd><p>Similar to the previous one, this only inserts a wait state in
the first 'write' of a given burst. reads are not
affected. This is the default behaviour of the server.</p>
<dt><b>Option "write_wait" (OTI087)</b><dd><p>This configures the VLB interface to add one wait state to
each write cycle.</p>
<dt><b>Option "read_wait" (OTI087)</b><dd><p>This configures the VLB interface to add one wait state to
each read cycle.</p>
<dt><b>Option "all_wait" (OTI087)</b><dd><p>Enables the slowest VLB transfer adding wait states in all
cases. Hopefully, no board will need this enabled.</p>
<dt><b>Option "one_wait" (OTI087)</b><dd><p>Sets the VLB interface to at least one wait state.</p>
<dt><b>Option "noaccel" (OTI087)</b><dd><p>One accelerated routine has been lately added to the driver,
allowing it to draw solid fills quite faster. This routine
only works (up to date) on segmented addressing, and only if
the virtual width is 1024. This option is automatically enabled
by the driver. Use this option if you want to disable it.</p>
</dl>
</p>
<p>As a rule of thumb, use the option "no_wait", and if it doesn't
result in corrupting text, lucky you. If not, try "first_wwait", and
downwards. ISA card owners should not use these options.</p>

 <HR NOSHADE>
<A HREF="Oak.html"><EM>Information for Oak Technologies Inc. Chipset Users</EM></A>
 <b>:</b> <EM>XF86Config options </EM><BR>
<b>Previous:</b> <A HREF="Oak1.html"><EM>Supported chipsets </EM></A><BR>
<b>Next:</b> <A HREF="Oak3.html"><EM>Mode issues </EM></A>



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