             Information for Oak Technologies Inc. Chipset Users

             Jorge F. Delgado Mendoza (delgadomendoza.j@pg.com)

                               17 August 1999

1.  Supported chipsets

The driver is used in the 8-bit / 256-color SVGA server and the mono server.
The following chipsets for Oak Tech. Inc. are supported:

      OTI037C
            8-bit VGA chipset, with up to 256Kbytes of DRAM. All the boards I
            have seen are only able to do standard VGA modes.  (ie. up to
            320x200x256 and up to 640x480x16). Currently the probe for this
            chip is disabled, so use the generic VGA driver instead.

      OTI067
            ISA SVGA chipset, up to 512Kbytes of DRAM (usually 70/80 ns).

      OTI077
            Enhanced version of the 067, with support for 1Mbyte and up to 65
            Mhz dot-clock. This chipset is capable of resolutions up to
            1024x768x256 colors in Non-Interlaced mode, and up to
            1280x1024x16 colors Interlaced.

      OTI087
            One of the first VLB chipsets available, it has a 16-bit external
            data path, and a 32-bit internal memory-controller data path. It
            features some acceleration hardware: register-based color expan-
            sion, hardware cursor, a primitive BitBlt engine, a 64 bit
            graphic latch and some other new (on its time) features.  Maximum
            BIOS resolutions are 1024x768x256 Non-Interlaced and
            1280x1024x256 interlaced. Maximum Dot-Clock is 80Mhz, but is usu-
            ally coupled with the OTI068 clock generator capable of frequen-
            cies up to 78Mhz.  This chipset supports up to 2MBytes of 70/70R
            ns DRAM.

      OTI107 and OTI111
            These are new, PCI chipsets by Oak Tech. Inc. Support is not
            included for them, as they are very rare and I haven't had the
            chance to look at one of these boards.  We have been unable to
            locate 107's. If anybody has such a board and can donate it to
            XFree86, we would be more than glad to add support for them.

            An OTI111 is now available and we are working on support for it.

All the chipsets up to the OTI087 are "Backwards compatible", in fact some
early drivers for the OTI087 based chipsets were those made for the 077.

Accelerated support is included only for OTI087 chipsets, also Mono server is
only included for 067/077 chipsets.

2.  XF86Config options

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).

      Option "linear" (OTI087)
            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.

            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.

      Option "fifo_aggressive" (OTI087)
            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.

      Option "fifo_conservative" (OTI087)
            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 anoma-
            lies on the screen.

      Option "enable_bitblt" (OTI087)
            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.

      Option "clock_50" (OTI087)
            This one will force the internal speed to 50 Mhz.

      Option "clock_66" (OTI087)
            This one will force the internal speed to 66 Mhz, speeding up
            performance of the chipset.

      Option "no_wait" (OTI087)
            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.

      Option "first_wait" (OTI087)
            Makes the VLB interface to add one wait state to the first read
            or write of a given burst.

      Option "first_wwait" (OTI087)
            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.

      Option "write_wait" (OTI087)
            This configures the VLB interface to add one wait state to each
            write cycle.

      Option "read_wait" (OTI087)
            This configures the VLB interface to add one wait state to each
            read cycle.

      Option "all_wait" (OTI087)
            Enables the slowest VLB transfer adding wait states in all cases.
            Hopefully, no board will need this enabled.

      Option "one_wait" (OTI087)
            Sets the VLB interface to at least one wait state.

      Option "noaccel" (OTI087)
            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 vir-
            tual width is 1024. This option is automatically enabled by the
            driver. Use this option if you want to disable it.

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.

3.  Mode issues

The use of very high dot-clocks has a REAL negative effect on the performance
of the boards, due to its limited 80Mbit/sec, higher dot clocks limit its
ability to draw data into the framebuffer. Thus expect better performance of
a 72Mhz based mode than on a 78Mhz based one (for example) where more band-
width is required for screen refresh.

It does not make much sense to use the highest clock (78 MHz) for 1024x768 at
76 Hz on a OTI087; the card will almost come to a standstill. A 72 MHz dot
clock results in 70 Hz which should be acceptable. If you have a monitor that
supports 1024x768 at 76 Hz with a 78 MHz dot clock, a standard OTI087 based
card is a poor match anyway.

4.  Linear addressing

Linear addressing is hardwired to 14 Mbytes for ISA boards and 78 Mbytes for
VLB boards, thus if you have more than that on your board you shouldn't
enable it.  The aperture is selected from the VideoRam parameter of the
XF86Config or from the amount of memory that is detected if VideoRam is not
found.

I hope (because I have not tested it very thoroughly) that linear addressing
will work on all ISA boards, VLB ones work flawlessly.

     Generated from XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/Oak.sgml,v 3.12.2.4 1999/08/18 13:12:11 hohndel Exp $

     $XConsortium: Oak.sgml /main/8 1996/05/12 20:58:00 kaleb $

