path: root/xc/programs/Xserver/hw/xfree86/doc/sgml/chips.sgml

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<article>

<!-- Title information -->
<title> Information for Chips and Technologies Users
<author> David Bateman (<it>dbateman@eng.uts.edu.au</it>),
         Egbert Eich (<it>Egbert.Eich@Physik.TH-Darmstadt.DE</it>)
<date> 19th July 1999

<ident>
$XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/chips.sgml,v 3.29 1999/08/28 11:18:16 dawes Exp $
</ident>

<!-- Table of contents -->
<toc>

<sect> Introduction <p>

With the release of XFree86 version &relvers;, the Chips and Technologies
driver has been extensively rewritten and contains many new features.
This driver must be considered work in progress, and those users
wanting stability are encouraged to use the older XFree86 3.3.x
versions. However this version of the Chips and Technologies driver
has many new features and bug fixes that might make users prefer
to use this version. These features include

<itemize>
<item>The long standing black/blue screen problem that some people have
	had should be fixed.
<item>Hardware/Software cursor switching on the fly, that should fix
	many of the known hardware cursor problems.
<item>Gamma correction at all depths and DirectColor visuals for depths of
	15 or greater with the HiQV series of chipsets.
<item>Supports PsuedoColor overlays on 16bpp TrueColor screens for HiQV.
<item>32bpp pixmaps while using a framebuffer in 24bpp packed pixel mode.
<item>Heaps more acceleration.
<item>1/4bpp support.
<item>Multihead
<item>Much more...
</itemize>

This document attempts to discuss the features of this driver, the
options useful in configuring it and the known problems. Most of the
Chips and Technologies chipsets are supported by this driver to some
degree.

<sect> Supported Chips <p>

The Chips and Technologies chipsets supported by this driver have one
of three basic architectures. A basic architecture, the WinGine architecture
which is a modification on this basic architecture and a completely new
HiQV architecture.

<sect1>Basic architecture<p>
<descrip>
<tag>ct65520</tag>
	(Max Ram: 1Mb, Max Dclk: 68MHz@5V)
<tag>ct65525</tag>
        This chip is basically identical to the 65530. It has the same
	ID and is identified as a 65530 when probed. See ct65530 for
	details.
<tag>ct65530</tag>
	This is a very similar chip to the 65520. However it additionally
	has the ability for mixed 5V and 3.3V operation and linear addressing
	of the video memory.
	(Max Ram: 1Mb, Max Dclk: 56MHz@3.3V, 68MHz@5V)
<tag>ct65535</tag>
	This is the first chip of the ct655xx series to support fully
	programmable clocks. Otherwise it has the the same properties
	as the 65530.
<tag>ct65540</tag>
	This is the first version of the of the ct655xx that was capable
	of supporting Hi-Color and True-Color. It also includes a fully
	programmable dot clock and supports all types of flat panels.
	(Max Ram: 1Mb, Max Dclk: 56MHz@3.3V, 68MHz@5V)
<tag>ct65545</tag>
	The chip is very similar to the 65540, with the addition of H/W
	cursor, pop-menu acceleration, BitBLT and support of PCI Buses.
	PCI version also allow all the BitBLT and H/W cursor registers
	to be memory mapped 2Mb above the Base Address.
	(Max Ram: 1Mb, Max Dclk: 56MHz@3.3V,68MHz@5V)
<tag>ct65546</tag>
	This chip is specially manufactured for Toshiba, and so documentation
	is not widely available. It is believed that this is really just a
	65545 with a higher maximum dot-clock of 80MHz.
	(Max Ram: 1Mb?, Max Dclk: 80MHz?)
<tag>ct65548</tag>
	This chip is similar to the 65545, but it also includes XRAM support
	and supports the higher dot clocks of the 65546. 
	(Max Ram: 1Mb, Max Dclk: 80MHz)
</descrip>

<sect1>WinGine architecture<p>
<descrip>
<tag>ct64200</tag>
	This chip, also known as the WinGine, is used in video cards
        for desktop systems. It often uses external DAC's and programmable
	clock chips to supply additional functionally. None of these are
	currently supported within the driver itself, so many cards will only
	have limited support. Linear addressing is not supported for this
	card in the driver.
	(Max Ram: 2Mb, Max Dclk: 80MHz)
<tag>ct64300</tag>
	This is a more advanced version of the WinGine chip, with specification
	very similar to the 6554x series of chips. However there are many
	differences at a register level. A similar level of acceleration to
	the 65545 is included for this driver.
	(Max Ram: 2Mb, Max Dclk: 80MHz)
</descrip>

<sect1>HiQV Architecture<p>
<descrip>
<tag>ct65550</tag>
	This chip includes many new features, including improved BitBLT
	support (24bpp color expansion, wider maximum pitch, etc), Multimedia
	unit (video capture, zoom video port, etc) and 24bpp uncompressed true
	color (i.e 32bpp mode). Also memory mapped I/O is possible on all bus
	configurations. 
	(Max Ram: 2Mb, Max Dclk: 80MHz@3.3V,100MHz@5V)
<tag>ct65554</tag>
	This chip is similar to the 65550 but has a 64bit memory bus as 
	opposed to a 32bit bus. It also has higher limits on the maximum
	memory and pixel clocks
	(Max Ram: 4Mb, Max Dclk: 100MHz@3.3V)
<tag>ct65555</tag>
	Similar to the 65554 but has yet higher maximum memory and pixel
	clocks. It also includes a new DSTN dithering scheme that improves
	the performance of DSTN screens.
	(Max Ram: 4Mb, Max Dclk: 110MHz@3.3V)
<tag>ct68554</tag>
	Similar to the 65555 but also incorporates "PanelLink" drivers. This
	serial link allows an LCD screens to be located up to 100m from the 
	video processor. Expect to see this chip soon in LCD desktop machines
	(Max Ram: 4Mb, Max Dclk: 110MHz@3.3V)
<tag>ct69000</tag>
	Similar to the 65555 but incorporates 2Mbytes of SGRAM on chip. It is
	the first Chips and Technologies chipset where all of the registers
	are accessible through MMIO, rather than just the BitBlt registers.
	(Max Ram: 2Mb Only, Max Dclk: 130MHz@3.3V)
<tag>ct69030</tag>
	Similar to the 69000 but incorporates 4Mbytes of SGRAM on chip and has
	faster memory and pixel clock limits. Also includes a second display
	channel so that the CRT can display independently of the LCD.
	(Max Ram: 4Mb Only, Max Dclk: 170MHz@3.3V)
</descrip>


<sect> XF86Config Options <p>

The following options are of particular interest to the Chips and
Technologies driver. It should be noted that the options are case
insensitive, and that  white space and "_" characters are ignored.
There are therefore a wide variety of possible forms for all options.
The forms given below are the preferred forms.

Options related to drivers can be present in the Screen, Device and
Monitor sections and the Display subsections.  The order of precedence
is Display, Screen, Monitor, Device. 

<descrip>
<tag>
Option "NoAccel"
</tag>
        This option will disable the use of any accelerated functions.
        This is likely to help with some problems related to DRAM
        timing, high dot clocks, and bugs in accelerated functions, at
        the cost of performance (which will still be reasonable on VLB/PCI).
<tag>
VideoRam 1024 (or another value)
</tag>
        This option will override the detected amount of video memory,
        and pretend the given amount of memory is present on the card.
<tag>
Option "NoLinear"
</tag>
	By default linear addressing is used on all chips where it
	can be set up automatically. The exception is for depths of
	1 or 4bpp where linear addressing is turned off by default.
	It is possible to turn the linear addressing off with this
	option. Note that H/W acceleration is only supported with
	linear addressing.
<tag>
Option "Linear"
</tag>
	When the chipset is capable of linear addressing and it has
	been turned off by default, this option can be used to turn it
	back on. This is useful for the 65530 chipset where the base
	address of the linear framebuffer must be supplied by the user,
	or at depths 1 and 4bpp. Note that linear addressing at 1 and 4bpp
	is not guaranteed to work correctly.
<tag>
MemBase 0x03b00000 (or a different address)
</tag>
        This sets the physical memory base address of the linear
        framebuffer. Typically this is probed correctly, but if
	you believe it to be mis-probed, this option might help.
	Also for non PCI machines specifying this force the linear base
	address to be this value, reprogramming the video processor
	to suit. Note that for the 65530 this is required as the
	base address can't be correctly probed.
<tag>
Option "HWcursor"
</tag>
	For chipsets that support hardware cursors, this option enforces
	their use, even for cases that are known to cause problems on some
	machines. Note that it is overridden by the "<tt>SWcursor</tt>"
	option. Hardware cursors effectively speeds all graphics operations
	as the job of ensuring that the cursor remains on top is now given
	to the hardware. It also reduces the effect of cursor flashing during
	graphics operations.
<tag>
Option "SWcursor"
</tag>
	This disables use of the hardware cursor provided by the chip.
	Try this if the cursor seems to have problems. 
<tag>
Option "STN"
</tag>
	The server is unable to differentiate between SS STN 
 	and TFT displays. This forces it to identify the display
	as a SS STN rather than a TFT.
<tag>
Option "UseModeline"
</tag>
	The flat panel timings are related to the panel size and not the
	size of the mode specified in XF86Config. For this reason the
	default behaviour of the server is to use the panel timings already
	installed in the chip. The user can force the panel timings to be
	recalculated from the modeline with this option. However the panel
	size will still be probed.
<tag>
Option "FixPanelSize"
</tag>
	For some machines the LCD panel size is incorrectly probed from
	the registers. This option forces the LCD panel size to be
	overridden by the modeline display sizes. This will prevent the
	use of a mode that is a different size than the panel. Before
	using this check that the server reports an incorrect panel
	size. This option can be used in conjunction with the option
	"UseModeline" to program all the panel timings using
	the modeline values.
<tag>
Option "NoStretch"
</tag>
	When the size of the mode used is less than the panel size, the
	default behaviour of the server is to stretch the mode in an attempt
	to fill the screen. A "<tt>letterbox</tt>" effect with no stretching
	can be achieved using this option.
<tag>
Option "LcdCenter"
</tag>
	When the size of the mode used is less than the panel size, the
	default behaviour of the server is to align the left hand edge of
	the display with the left hand edge of the screen. Using this option
	the mode can be centered in the screen. This option is reported to
	have problems with some machines at 16/24/32bpp, the effect of which
	is that the right-hand edge of the mode will be pushed off the screen.
<tag>
Option "HWclocks"
</tag>
	For the chips either using the WinGine or basic architectures, the
	chips generates a number of fixed clocks internally. With the chips
	65535 and later or the 64300, the default is to use the programmable
	clock for all clocks. It is possible to use the fixed clocks
	supported by the chip instead by using this option. Typically
	this will give you some or all of the clocks 25.175, 28.322,
	31.000 and 36.000MHz. The current programmable clock will be
	given as the last clock in the list. On a cold-booted system this
	might be the appropriate value to use at the text console (see the 
	"<tt>TextClockFreq</tt>" option), as many flat panels will need a
	dot clock different than the default to synchronise. The
	programmable clock makes this option obsolete and so it's use
	isn't recommended. It is completely ignored for HiQV chipsets.
<tag>
Option "UseVclk1"
</tag>
	The HiQV series of chips have three programmable clocks. The
	first two are usually loaded with 25.175 and 28.322MHz for
	VGA backward compatibility, and the third is used as a fully
	programmable clock. On at least one system (the Inside 686 LCD/S
	single board computer) the third clock is unusable. This option
	forces the use of VClk1 as the programmable clock.
<tag>
TextClockFreq 25.175
</tag>
	Except for the HiQV chipsets, it is impossible for the server to read
	the value of the currently used frequency for the text console when
	using programmable clocks. Therefore the server uses a default value of
	25.175MHz as the text console clock. For some LCDs, in particular
	DSTN screens, this clock will be wrong. This allows the user to
	select a different clock for the server to use when returning to
	the text console.
<tag>
Option "FPClock8"   "65.0"
Option "FPClock16"  "65.0"
Option "FPClock24"  "65.0"
Option "FPClock32"  "65.0"
</tag>
	In general the LCD panel clock should be set independently of the
	modelines supplied. Normally the chips BIOS set the flat panel
	clock correctly and so the default behaviour with HiQV chipset is
	to leave the flat panel clock alone, or force it to be 90% of the
	maximum allowable clock if the current panel clock exceeds the
	dotclock limitation due to a depth change. This option allows the user
	to force the server the reprogram the flat panel clock independently
	of the modeline with HiQV chipset. The four options are for 8bpp or
	less, 16, 24 or 32bpp LCD panel clocks, where the options above set
	the clocks to 65MHz.
<tag>
Option "MMIO"
</tag>
	This has a different effect depending on the hardware on which it
	is used. For the 6554x machines MMIO is only used to talk to the
	BitBLT engine and is only usable with  PCI buses. It is enabled
	by default for 65545 machines since the blitter	can not be used
	otherwise. The HiQV series of chipsets must use MMIO with their
	BitBLT engines, and so this is enabled by default. However the
	690xx chipsets can use MMIO for all communications with the video
	processor. So using this option on a 690xx chipset forces them
	to use MMIO for all communications. This only makes sense when
	the 690xx is on a PCI bus so that normal PIO can be disabled.
	(WARNING!! 690xx MMIO is untested)
<tag>
Option "SuspendHack"
</tag>
	This option sets the centering and stretching to the BIOS
	default values. This can fix suspend/resume problems on some
	machines. It overrides the options "LcdCenter" 
	and "NoStretch".
<tag>
Option "18bitBus"  (Chips 65540/45/46/48)
</tag>
	For 24bpp on TFT screens, the server assumes that a 24bit bus
	is being used. This can result in a reddish tint to 24bpp mode.
	This option, selects an 18 bit TFT bus. For other depths this
	option has no effect.
<tag>
Chipset "ct65546" (or some other chip)
</tag>
	It is possible that the chip could be misidentified, particular
	due to interactions with other drivers in the server. It is
	possible to force the server to identify a particular chip with
	this option.
<tag>
Option "SyncOnGreen"
</tag>
	Composite sync on green. Possibly useful if you wish to use an
	old workstation monitor. The HiQV internal RAMDAC's supports
	this mode of operation, but whether a particular machine does
	depends on the manufacturer. 
<tag>
DacSpeed 80.000
</tag>
	The server will limit the maximum dotclock to a value as specified
	by the manufacturer. This might make certain modes impossible
	to obtain with a reasonable refresh rate. Using this option the
	user can override the maximum dot-clock and specify any value they
	prefer. Use caution with this option, as driving the video processor
	beyond its specifications might cause damage.
<tag>
Option "SetMClk" "38.000MHz"
Option "SetMClk" "38000kHz"
</tag>
	This option sets the internal memory clock (MCLK) registers of HiQV
	chipsets to 38MHz or some other value. Use caution as excess heat
	generated by the video processor if its specifications are exceeded
	might cause damage. However careful use of this option might boost
	performance. This option might also be used to reduce the speed of
	the memory clock to preserve power in modes that don't need the full
	speed of the memory to work correctly. This option might also be
	needed to reduce the speed of the memory clock with the
	"<tt>Overlay</tt>" option. 
<tag>
Option "RGBbits"  "8"
</tag>
	By default it is assumed that there are 6 significant bits in the
	RGB representation of the colours in 4bpp and above. If the colours
	seem darker than they should be, perhaps your ramdac is has 8
	significant bits. This option forces the server to assume that there
	are 8 significant bits.
<tag>
Option "ShowCache"
</tag>
	This is a debugging option and general users have no need of it.
	Using this option, when the virtual desktop is scrolled away from
	the zero position, the pixmap cache becomes visible. This is useful
	to see that pixmaps, tiles, etc have been properly cached.
<tag>
Option "ShadowFB"
</tag>
	This option is only useful when acceleration can't be used and linear
	addressing can be used. With this option all of the graphics are
	rendered into a copy of the framebuffer that is keep in the main memory
	of the computer, and the screen is updated from this copy. In this
	way the expensive operation of reading back to contents of the screen
	is never performed and the performance is improved. Because the
	rendering is all done into a virtual framebuffer acceleration can not
	be used.
<tag>
Option "Overlay"
</tag>
	The HiQV chipsets contain a multimedia engine that allow a 16bpp
	window to be overlayed on the screen. This driver uses this capability
	to include a 16bpp framebuffer on top of an 8bpp framebuffer. In this
	way PseudoColor and TrueColor visuals can be used on the same screen.
	XFree86 believes that the 8bpp framebuffer is overlayed on the 16bpp
	framebuffer. Therefore to use this option the server must be started
	in either 15 or 16bpp depth. Also the maximum size of the desktop 
	with this option is 1024x1024, as this is the largest window that the
	HiQV multimedia engine can display. Note that this option using the
	multimedia engine to its limit, and some manufacturers have set a
	default memory clock that will cause pixel errors with this option.
	If you get pixel error with this option try using the
	"<tt>SetMClk</tt>" option to slow the memory clock.
<tag>
Option "ColorKey" "255" 
</tag>
	Normally the color transparency key for the overlay is the 8bpp lookup
	table entry 255. This might cause troubles with some applications, and
	so this option allows the color transparency key to be set to some
	other value. Legal values are 2 to 255 inclusive.
<tag>
Option "XaaNoScreenToScreenCopy",
Option "XaaNoSolidFillRect",
Option "XaaNoSolidHorVertLine",
Option "XaaNoMono8x8PatternFillRect",
Option "XaaNoColor8x8PatternFillRect",
Option "XaaNoCPUToScreenColorExpandFill", 
Option "XaaNoScreenToScreenColorExpandFill",
Option "XaaNoImageWriteRect",
Option "XaaNoImageReadRect",
Option "XaaNoPixmapCache",
Option "XaaNoOffscreenPixmaps" 
</tag>
	These option individually disable the features of the XAA acceleration
	code that the Chips and Technologies driver uses. If you have a problem
	with the acceleration and these options will allow you to isolation 
	the problem. This information will be invaluable in debugging any
	problems.
</descrip>

<sect> Modelines <p>

When constructing a modeline for use with the Chips and Technologies
driver you'll needed to considered several points

<descrip>
<tag> * Virtual Screen Size </tag>
		It is the virtual screen size that determines the amount
	of memory used by a mode. So if you have a virtual screen size
	set to 1024x768 using a 800x600 at 8bpp, you use 768kB for the
	mode. Further to this some of the XAA acceleration requires that
	the display pitch is a multiple of 64 pixels. So the driver will
	attempt to round-up the virtual X dimension to a multiple of 64,
	but leave the virtual resolution untouched. This might further
	reduce the available memory.
<tag> * 16/24/32 Bits Per Pixel </tag>
		Hi-Color and True-Color modes are implemented in the
	server. The clocks in the 6554x series of chips are internally
	divided by 2 for 16bpp and 3 for 24bpp, allowing one modeline to
	be used at all depths.  The effect of this is that the maximum
	dot clock visible to the user is a half or a third of the value
	at 8bpp. The HiQV series of chips doesn't need to use additional
	clock cycles to display higher depths, and so the same modeline
	can be used at all depths, without needing to divide the clocks.
	Also 16/24/32 bpp modes will need 2 , 3 or 4 times respectively more
	video ram.
<tag> * Frame Acceleration</tag>
		Many DSTN screens use frame acceleration to improve the
	performance of the screen. This can be done by using an external
	frame buffer, or incorporating the framebuffer at the top of video
	ram depending on the particular implementation. The Xserver assumes
	that the framebuffer, if used, will be at the top of video ram.
	The amount of ram required for the framebuffer will vary depending
	on the size of the screen, and will reduce the amount of video
	ram available to the modes. Typical values for the size of the
	framebuffer will be 61440 bytes (640x480 panel), 96000 bytes
	(800x600 panel) and 157287 bytes (1024x768 panel).
<tag> * H/W Acceleration </tag>
		The H/W cursor will need 1kB for the 6554x and 4kb for the
	65550. On the 64300 chips the H/W cursor is stored in registers and
	so no allowance is needed for the H/W cursor. In addition to this
	many graphics operations are speeded up using a
	"<tt>pixmap cache</tt>". Leaving too little memory available for
	the cache will only have a detrimental effect on the graphics
	performance.
<tag> * PseudoColor Overlay </tag>
		If you use the "<tt>overlay</tt>" option, then there are
	actually two framebuffers in the video memory. An 8bpp one and a
	16bpp one. The total memory requirements in this mode of operation
	is therefore similar to a 24bpp mode. The overlay consumes memory
	bandwidth, so that the maximum dotclock will be similar to a 24bpp
	mode.
<tag> * VESA like modes </tag>
		We recommend that you try and pick a mode that is similar
	to a standard VESA mode. If you don't a suspend/resume or LCD/CRT
	switch might mess up the screen. This is a problem with the video
	BIOS not knowing about all the funny modes that might be selected.
<tag> * Dot Clock </tag>
		For LCD screens, the lowest clock that gives acceptable
	contrast and flicker is usually the best one. This also gives
	more memory bandwidth for use in the drawing operations. Some
	users prefer to use clocks that are defined by their BIOS. This
	has the advantage that the BIOS will probably restore the clock
	they specified after a suspend/resume or LCD/CRT switch. For a
	complete discussion on the dot clock limitations, see the next
	section.
</descrip>

The driver is capable of driving both a CRT and a flat panel
display. In fact the timing for the flat panel are dependent on the
specification of the panel itself and are independent of the particular
mode chosen. For this reason it is recommended to use one of the programs
that automatically generate XF86Config files, such as "<tt>xf86config</tt>"
or "<tt>XF86Setup</tt>".

However there are many older machines, particularly those with 800x600
screen or larger, that need to reprogram the panel timings. The reason
for this is that the manufacturer has used the panel timings to get a
standard EGA mode to work on flat panel, and these same timings don't
work for an SVGA mode. For these machines the "<tt>UseModeline</tt>"
and/or possibly the "<tt>FixPanelSize</tt>" option might be needed. Some
machines that are known to need these options include.

<quote><verb>
Modeline "640x480@8bpp"	  25.175  640  672  728  816   480  489  501  526
Modeline "640x480@16bpp"  25.175  640  672  728  816   480  489  501  526
Options: "UseModeline"
Tested on a Prostar 8200, (640x480, 65548, 1Mbyte)
</verb></quote>

<quote><verb>
Modeline "800x600@8bpp"	  28.322  800  808  848  936   600  600  604  628
Options: "FixPanelSize", "UseModeline"
Tested on a HP OmniBook 5000CTS (800x600 TFT, 65548, 1Mbyte)
</verb></quote>

<quote><verb>
Modeline "800x600@8bpp"	  30.150  800  896  960 1056   600  600  604  628
Options: "FixPanelSize", "UseModeline"
Test on a Zeos Meridan 850c (800x600 DSTN, 65545, 1Mbyte)
</verb></quote>

The NEC Versa 4080 just needs the "FixPanelSize" option. To the best of my
knowledge no machine with a HiQV needs the "UseModeline" or "FixPanelSize"
options.

<sect> The Full Story on Clock Limitations <p>

There has been much confusion about exactly what the clock limitations
of the Chips and Technologies chipsets are. Hence I hope that this
section will clear up the misunderstandings. 

In general there are two factors determining the maximum dotclock.
There is the limit of the maximum dotclock the video processor can handle, 
and there is another limitation of the available memory bandwidth. The 
memory bandwidth is determined by the clock used for the video memory.
For chipsets incapable of colour depths greater that 8bpp like the 65535,
the dotclock limit is solely determined by the highest dotclock the video
processor is capable of handling. So this limit will be either 56MHz or
68MHz for the 655xx chipsets, depending on what voltage they are driven
with, or 80MHz for the 64200 WinGine machines.

The 6554x and 64300 WinGine chipsets are capable of colour depths of 16
or 24bpp. However there is no reliable way of probing the memory clock
used in these chipsets, and so a conservative limit must be taken for
the dotclock limit. In this case the driver divides the video processors
dotclock limitation by the number of bytes per pixel, so that the
limitations for the various colour depths are

<verb>
                        8bpp    16bpp   24bpp
64300                   85      42.5    28.33
65540/65545 3.3v        56      28      18.67
65540/65545 5v          68      34      22.67
65546/65548             80      40      26.67
</verb>

For a CRT or TFT screen these limitations are conservative and the user
might safely override them with the "<tt>DacSpeed</tt>" option to some
extent. However these numbers take no account of the extra bandwidth 
needed for DSTN screens. 

For the HiQV series of chips, the memory clock can be successfully probed.
Hence you will see a line like

<verb>
(--) CHIPS(0): Probed memory clock of  40.090 MHz
</verb>

in your startx log file. Note that many chips are capable of higher
memory clocks than actually set by BIOS. You can use the "<tt>SetMClk</tt>"
option in your XF86Config file to get a higher MClk. However some
video ram, particularly EDO, might not be fast enough to handle this,
resulting in drawing errors on the screen. The formula to determine the
maximum usable dotclock on the HiQV series of chips is

<verb>
Max dotclock = min(MaxDClk,  0.70  * 4 * MemoryClk / (BytesPerPixel + 
                (isDSTN == TRUE ? 1 : 0)))
</verb>

which says that there are two limits on the dotclock. One the overall
maximum, and another due to the available memory bandwidth of the chip.
For the memory bandwidth 4 bytes are transfered every clock cycle (Hence
the 4), but after accounting for the RAS/CAS signaling only about 70%
of the bandwidth is available. The whole thing is divided by the bytes
per pixel, plus an extra byte if you are using a DSTN. The extra byte
with DSTN screens is used for the frame buffering/acceleration in these
screens. So for the various Chips and Technologies chips the maximum
specifications are

<verb>
                    Max DClk MHz      Max Mem Clk MHz
65550 rev A 3.3v          80                38 
65550 rev A 5v           110                38
65550 rev B               95                50
65554                     94.5              55
65555                    110                55
68554                    110                55
69000                    135                83
69030                    170               100
</verb>

Note that all of the chips except the 65550 rev A are 3.3v only. Which
is the reason for the drop in the dot clock. Now the maximum memory clock
is just the maximum supported by the video processor, not the maximum
supported by the video memory. So the value actually used for the memory
clock might be significantly less than this maximum value. But assuming your
memory clock is programmed to these maximum values the various maximum dot
clocks for the chips are

<verb>
                        ------CRT/TFT-------    --------DSTN--------
                        8bpp    16bpp   24bpp   8bpp    16bpp   24bpp
65550 rev A 3.3v        80      53.2    35.47   53.2    35.47   26.6
65550 rev A 5v          106.2   53.2    35.47   53.2    35.47   26.6
65550 rev B             95      70      46.67   70      46.67   35.0
65554                   94.5    77      51.33   77      51.33   38.5
65555                   110     77      51.33   77      51.33   38.5
68554                   110     77      51.33   77      51.33   38.5
69000                   135    116.2    77.47  116.2    77.47   58.1
69030                   170    140      93.33  140      93.33   70
</verb>

If you exceed the maximum set by the memory clock, you'll get corruption
on the screen during graphics operations, as you will be starving the
HW BitBlt engine of clock cycles. If you are driving the video memory
too fast (too high a MemClk) you'll get pixel corruption as the data
actually written to the video memory is corrupted by driving the memory
too fast. You can probably get away with exceeding the Max DClk at 8bpp
on TFT's or CRT's by up to 10% or so without problems, it will just generate
more heat, since the 8bpp clocks aren't limited by the available memory
bandwidth.

If you find you truly can't achieve the mode you are after with the default
clock limitations, look at the options "<tt>DacSpeed</tt>" and 
"<tt>SetMClk</tt>". Using these should give you all the capabilities
you'll need in the server to get a particular mode to work. However use
caution with these options, because there is no guarantee that driving the
video processor beyond it capabilities won't cause damage.

<sect> Troubleshooting <p>

<descrip>
<tag> The cursor appears as a white box, after switching modes</tag>
	There is a known bug in the H/W cursor, that sometimes causes
	the cursor to be redrawn as a white box, when the mode is changed.
	This can be fixed by moving the cursor to a different region,
	switching to the console and back again, or if it is too annoying
	the H/W cursor can be disabled by removing the "<tt>HWcursor</tt>"
	option.
<tag> The cursor hot-spot isn't at the same point as the cursor</tag>
 	With modes on the 6555x machines that are stretched to fill the
	flat panel, the H/W cursor is not correspondingly stretched. This
	is a small and long-standing bug in the current server. You can
	avoid this by either using the "<tt>NoStretch</tt>" option or
	removing the <tt>HWcursor</tt>" option.
<tag> The lower part of the screen is corrupted</tag>
	Many DSTN screens use the top of video ram to implement a frame
	accelerator. This reduces the amount of video ram available to
	the modes. The server doesn't prevent the user from specifying
	a mode that will use this memory, it prints a warning on the console.
	The effect of this problem will be that the lower part of the screen
	will reside in the same memory as the frame accelerator and will
	therefore be corrupt. Try reducing the amount of memory consumed
	by the mode.
<tag> There is a video signal, but the screen doesn't sync.</tag>
        You are using a mode that your screen cannot handle. If it is a
        non-standard mode, maybe you need to tweak the timings a bit. If
        it is a standard mode and frequency that your screen should be
        able to handle, try to find different timings for a similar mode
        and frequency combination. For LCD modes, it is possible that your
	LCD panel requires different panel timings at the text console than
	with a graphics mode. In this case you will need the
	"<tt>UseModeline</tt>" and perhaps also the "<tt>FixPanelSize</tt>"
	options to reprogram the LCD panel timings to sensible values.
<tag> `Wavy' screen.</tag>
        Horizontal waving or jittering of the whole screen, continuously
        (independent from drawing operations).  You are probably using a
        dot clock that is too high (or too low); it is also possible that
	there is interference with a close MCLK. Try a lower dot clock.
	For CRT's you can also try to tweak the mode timings; try increasing
        the second horizontal value somewhat.
<tag> Crash or hang after start-up (probably with a black screen).</tag>
        Try the "<tt>NoAccel</tt>" or one of the XAA acceleration options
	discussed above. Check that the BIOS settings are OK; in particular,
	disable caching of 0xa0000-0xaffff. Disabling hidden DRAM refresh
	may also help.
<tag> Hang as the first text is appearing on the screen on SVR4 machines.</tag>
        This problem has been reported under UnixWare 1.x, but not tracked
        down. It doesn't occur under UnixWare 2.x and only occurs on the
        HiQV series of chips. It might affect some other SVR4 operating
        systems as well. The workaround is to turn off the use of CPU to
        screen acceleration with the
	"<tt>XaaNoCPUToScreenColorExapndFill</tt>" option.
<tag> Crash, hang, or trash on the screen after a graphics operation.</tag>
        This may be related to a bug in one of the accelerated
        functions, or a problem with the BitBLT engine. Try the
        "<tt>NoAccel</tt>" or one of the XAA acceleration options
	discussed above. Also check the BIOS settings. It is also possible
	that with a high dot clock and depth on a large screen there is
	very little bandwidth left for using the BitBLT engine. Try
	reducing the clock.
<tag> Chipset is not detected.</tag>
        Try forcing the chipset to a type that is most similar to what
        you have.
<tag>The screen is blank when starting X</tag>
	One possible cause of this problem with older linux kernels is that
	the "APM_DISPLAY_BLANK" option didn't work correct. Either upgrade
	your kernel or rebuild it with the "APM_DISPLAY_BLANK" option
	disabled. If the problem remains, or you aren't using linux, a
	CRT/LCD or switch to and from the virtual console will often fix it.
<tag> Textmode is not properly restored</tag>
        This has been reported on some configurations. Many laptops
	use the programmable clock of the 6554x chips at the console.
	It is not always possible to find out the setting that is
	used for this clock if BIOS has written the MClk after the
	VClk. Hence the server assumes a 25.175MHz clock at the
	console. This is correct for most modes, but can cause some
	problems. Usually this is fixed by switching between the LCD
	and CRT. Alternatively the user can use the "<tt>TextClockFreq</tt>"
	option described above to select a different clock for the
	text console. Another possible cause of this problem is if 
	linux kernels are compiled with the "APM_DISPLAY_BLANK" option.
	As mentioned before, try disabling this option.
<tag> I can't display 640x480 on my 800x600 LCD</tag>
	The problem here is that the flat panel needs timings that
	are related to the panel size, and not the mode size. There is
	no facility in the current Xservers to specify these values,
	and so the server attempts to read the panel size from the
	chip. If the user has used the "<tt>UseModeline</tt>" or
	"<tt>FixPanelSize</tt>" options the panel timings are derived
	from the mode, which can be different than the panel size. Try
	deleting theses options	from XF86Config or using an LCD/CRT switch.
<tag> I can't get a 320x240 mode to occupy the whole 640x480 LCD</tag>
	There is a bug in the 6554x's H/W cursor for modes that are
	doubled vertically. The lower half of the screen is not accessible.
	The servers solution to this problem is not to do doubling vertically.
	Which results in the 320x240 mode only expanded to 640x360. If this
	is a problem, a work around is to remove the "<tt>HWcursor</tt>"
	option. The server will then allow the mode to occupy the whole
	640x480 LCD.
<tag> After a suspend/resume my screen is messed up</tag>
	During a suspend/resume, the BIOS controls what is read and 
	written back to the registers. If the screen is using a mode
	that BIOS doesn't know about, then there is no guarantee that
	it will be resumed correctly. For this reason a mode that is
	as close to VESA like as possible should be selected. It is also
	possible that the VGA palette can be affected by a suspend/resume.
	Using an 8bpp, the colour will then be displayed incorrectly. This
	shouldn't affect higher depths, and is fixable with a switch to
	the virtual console and back.
<tag> The right hand edge of the mode isn't visible on the LCD</tag>
	This is usually due to a problem with the "<tt>LcdCenter</tt>"
	option. If this option is removed form XF86Config, then the problem
	might go away. Alternatively the manufacturer could have incorrectly
	programmed the panel size in the EGA console mode. The
	"<tt>FixPanelSize</tt>" can be used to force the modeline values into
	the panel size registers. Two machines that are known to have this
	problem are the "<tt>HP OmniBook 5000</tt>" and the "<tt>NEC  Versa
	4080</tt>".
<tag> My TFT screen has a reddish tint in 24bpp mode</tag>
	For 6554x chipsets the server assumes that the TFT bus width is
	24bits. If this is not true then the screen will appear to have a
	reddish tint. This can be fixed by using the "<tt>18BitBus</tt>"
	option. Note that the reverse is also true. If the "<tt>18BitBus</tt>"
	is used and the TFT bus width is 24bpp, then the screen will appear
	reddish. Note that this option only has an effect on TFT screens. 
<tag> SuperProbe won't work with my chipset</tag>
	At least one non-PCI bus system with a HiQV chipset has been found to
	require the "<tt>-no_bios</tt>" option for SuperProbe to correctly
	detect the chipset with the factory default BIOS settings. The server
	itself can correctly detect the chip in the same situation.
<tag> My 690xx machine lockups when using the "<tt>MMIO</tt>" option</tag>
	The 690xx MMIO mode has been implemented entirely from the manual
	as I don't have the hardware to test it on. At this point no testing
	has been done and it is entirely possible that the "<tt>MMIO</tt>
	option will lockup your machine. You have been warned! However if
	you do try this option and are willing to debug it, I'd like to hear
	from you.
<tag> My TrueColor windows are corrupted when using the "<tt>Overlay</tt>" option </tag>
	Chips and Technologies specify that the memory clock used with the
	multimedia engine running should be lower than that used without. As
	use of the HiQV chipsets multimedia engine was supposed to be for
	things like zoomed video overlays, its use was supposed to be
	occasional and so most machines have their memory clock set to a value
	that is too high for use with the "<tt>Overlay</tt>" option. So with 
	the "<tt>Overlay</tt>" option, using the "<tt>SetMClk</tt>" option to
	reduce the speed of the memory clock is recommended.
<tag> I can't start X-windows with 16, 24 or 32bpp</tag>
	Firstly, is your machine capable of 16/24/32bpp with the mode
	specified. Many LCD displays are incapable of using a 24bpp 
	mode. Also you need at least a 65540 to use 16/24bpp and at least a
	65550 for 32bpp. The amount of memory used by the mode will be
	doubled/tripled/quadrupled. The correct options to start the server
	with these modes are

<verb>
	  startx -- -depth 16             5-6-5 RGB ('64K color', XGA)
	  startx -- -depth 15             5-5-5 RGB ('Hicolor')
	  startx -- -depth 24             8-8-8 RGB truecolor
</verb>
	or with the HiQV series of chips you might try
<verb>
	  startx -- -depth 24 -fbbpp 32   8-8-8 RGB truecolor
</verb>
	however as XFree86 version &relvers; allows 32bpp pixmaps to be
	used with framebuffers operating in 24bpp, this mode of operating
	will cost performance for no gain in functionality.

	Note that the "<tt>-bpp</tt>" option has been removed
	and replaced with a "<tt>-depth</tt>" and "<tt>-fbbpp</tt>"
	option because of the confusion between the depth and number of
        bits per pixel used to represent to framebuffer and the pixmaps
        in the screens memory.
</descrip>

  A general problem with the server that can manifested in many way such
  as drawing errors, wavy screens, etc is related to the programmable
  clock. Many potential programmable clock register setting are unstable.
  However luckily there are many different clock register setting that
  can give the same or very similar clocks. The clock code can be fooled
  into giving a different and perhaps more stable clock by simply changing
  the clock value slightly. For example 65.00MHz might be unstable while
  65.10MHz is not. So for unexplained problems not addressed above, please
  try to alter the clock you are using slightly, say in steps of 0.05MHz
  and see if the problem goes away. Alternatively, using the
  "<tt>UseVClk1</tt>" option with HiQV chips might also help.


  For other screen drawing related problems, try the "<tt>NoAccel</tt>" or
  one of the XAA acceleration options discussed above. A useful trick for
  all laptop computers is to switch between LCD/CRT (usually with something
  like Fn-F5), if the screen is having problems.

  If you are having driver-related problems that are not addressed by this
  document, or if you have found bugs in accelerated functions, you can
  try contacting the XFree86 team (the current driver maintainer can be
  reached at <it>dbateman@eng.uts.edu.au</it> or 
  <it>Egbert.Eich@Physik.TH-Darmstadt.DE)</it>,
  or post in the Usenet newsgroup "<it>comp.windows.x.i386unix</it>".

<sect> Disclaimer <p>

XFree86, allows the user to do damage to their hardware with software.
Although the authors of this software have tried to prevent this, they
disclaim all responsibility for any damage caused by the software. Use
caution, if you think the Xserver is frying your screen, TURN THE COMPUTER
OFF!!

<sect> Acknowledgement <p>

The authors of this software wish to acknowledge the support
supplied by Chips and Technologies during the development of this
software.

<sect> Authors <p>

<tt>Major Contributors</tt> (In no particular order)
<itemize>
<item>Nozomi Ytow
<item>Egbert Eich
<item>David Bateman
<item>Xavier Ducoin
</itemize>

<tt>Contributors</tt> (In no particular order)
<itemize>
<item>Ken Raeburn
<item>Shigehiro Nomura
<item>Marc de Courville
<item>Adam Sulmicki
<item>Jens Maurer
</itemize>

We also thank the many people on the net who have contributed by reporting
bugs and extensively testing this server.

</article>