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 $