kernel-options.txt

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activate the given video mode at boot time and make it the default
mode, if the hardware allows. Currently defined names are:

 - stlow           : 320x200x4
 - stmid, default5 : 640x200x2
 - sthigh, default4: 640x400x1
 - ttlow           : 320x480x8, TT only
 - ttmid, default1 : 640x480x4, TT only
 - tthigh, default2: 1280x960x1, TT only
 - vga2            : 640x480x1, Falcon only
 - vga4            : 640x480x2, Falcon only
 - vga16, default3 : 640x480x4, Falcon only
 - vga256          : 640x480x8, Falcon only
 - falh2           : 896x608x1, Falcon only
 - falh16          : 896x608x4, Falcon only

  If no video mode is given on the command line, the kernel tries the
modes names "default<n>" in turn, until one is possible with the
hardware in use.

  A video mode setting doesn't make sense, if the external driver is
activated by a "external:" sub-option.

4.1.2) inverse
--------------

Invert the display. This affects both, text (consoles) and graphics
(X) display. Usually, the background is chosen to be black. With this
option, you can make the background white.

4.1.3) font
-----------

Syntax: font:<fontname>

Specify the font to use in text modes. Currently you can choose only
between `VGA8x8', `VGA8x16' and `PEARL8x8'. `VGA8x8' is default, if the
vertical size of the display is less than 400 pixel rows. Otherwise, the
`VGA8x16' font is the default.

4.1.4) hwscroll_
----------------

Syntax: hwscroll_<n>

The number of additional lines of video memory to reserve for
speeding up the scrolling ("hardware scrolling"). Hardware scrolling
is possible only if the kernel can set the video base address in steps
fine enough. This is true for STE, MegaSTE, TT, and Falcon. It is not
possible with plain STs and graphics cards (The former because the
base address must be on a 256 byte boundary there, the latter because
the kernel doesn't know how to set the base address at all.)

  By default, <n> is set to the number of visible text lines on the
display. Thus, the amount of video memory is doubled, compared to no
hardware scrolling. You can turn off the hardware scrolling altogether
by setting <n> to 0.

4.1.5) internal:
----------------

Syntax: internal:<xres>;<yres>[;<xres_max>;<yres_max>;<offset>]

This option specifies the capabilities of some extended internal video
hardware, like e.g. OverScan. <xres> and <yres> give the (extended)
dimensions of the screen.

  If your OverScan needs a black border, you have to write the last
three arguments of the "internal:". <xres_max> is the maximum line
length the hardware allows, <yres_max> the maximum number of lines.
<offset> is the offset of the visible part of the screen memory to its
physical start, in bytes.

  Often, extended interval video hardware has to be activated somehow.
For this, see the "sw_*" options below.

4.1.6) external:
----------------

Syntax:
  external:<xres>;<yres>;<depth>;<org>;<scrmem>[;<scrlen>[;<vgabase>\
           [;<colw>[;<coltype>[;<xres_virtual>]]]]]

[I had to break this line...]

  This is probably the most complicated parameter... It specifies that
you have some external video hardware (a graphics board), and how to
use it under Linux/m68k. The kernel cannot know more about the hardware
than you tell it here! The kernel also is unable to set or change any
video modes, since it doesn't know about any board internal. So, you
have to switch to that video mode before you start Linux, and cannot
switch to another mode once Linux has started.

  The first 3 parameters of this sub-option should be obvious: <xres>,
<yres> and <depth> give the dimensions of the screen and the number of
planes (depth). The depth is is the logarithm to base 2 of the number
of colors possible. (Or, the other way round: The number of colors is
2^depth).

  You have to tell the kernel furthermore how the video memory is
organized. This is done by a letter as <org> parameter:

 'n': "normal planes", i.e. one whole plane after another
 'i': "interleaved planes", i.e. 16 bit of the first plane, than 16 bit
      of the next, and so on... This mode is used only with the
	  built-in Atari video modes, I think there is no card that
	  supports this mode.
 'p': "packed pixels", i.e. <depth> consecutive bits stand for all
	  planes of one pixel; this is the most common mode for 8 planes
	  (256 colors) on graphic cards
 't': "true color" (more or less packed pixels, but without a color
	  lookup table); usually depth is 24

For monochrome modes (i.e., <depth> is 1), the <org> letter has a
different meaning:

 'n': normal colors, i.e. 0=white, 1=black
 'i': inverted colors, i.e. 0=black, 1=white

  The next important information about the video hardware is the base
address of the video memory. That is given in the <scrmem> parameter,
as a hexadecimal number with a "0x" prefix. You have to find out this
address in the documentation of your hardware.

  The next parameter, <scrlen>, tells the kernel about the size of the
video memory. If it's missing, the size is calculated from <xres>,
<yres>, and <depth>. For now, it is not useful to write a value here.
It would be used only for hardware scrolling (which isn't possible
with the external driver, because the kernel cannot set the video base
address), or for virtual resolutions under X (which the X server
doesn't support yet). So, it's currently best to leave this field
empty, either by ending the "external:" after the video address or by
writing two consecutive semicolons, if you want to give a <vgabase>
(it is allowed to leave this parameter empty).

  The <vgabase> parameter is optional. If it is not given, the kernel
cannot read or write any color registers of the video hardware, and
thus you have to set appropriate colors before you start Linux. But if
your card is somehow VGA compatible, you can tell the kernel the base
address of the VGA register set, so it can change the color lookup
table. You have to look up this address in your board's documentation.
To avoid misunderstandings: <vgabase> is the _base_ address, i.e. a 4k
aligned address. For read/writing the color registers, the kernel
uses the addresses vgabase+0x3c7...vgabase+0x3c9. The <vgabase>
parameter is written in hexadecimal with a "0x" prefix, just as
<scrmem>.

  <colw> is meaningful only if <vgabase> is specified. It tells the
kernel how wide each of the color register is, i.e. the number of bits
per single color (red/green/blue). Default is 6, another quite usual
value is 8.

  Also <coltype> is used together with <vgabase>. It tells the kernel
about the color register model of your gfx board. Currently, the types
"vga" (which is also the default) and "mv300" (SANG MV300) are
implemented.

  Parameter <xres_virtual> is required for ProMST or ET4000 cards where
the physical linelength differs from the visible length. With ProMST, 
xres_virtual must be set to 2048. For ET4000, xres_virtual depends on the
initialisation of the video-card.
If you're missing a corresponding yres_virtual: the external part is legacy,
therefore we don't support hardware-dependent functions like hardware-scroll,
panning or blanking.

4.1.7) eclock:
--------------

The external pixel clock attached to the Falcon VIDEL shifter. This
currently works only with the ScreenWonder!

4.1.8) monitorcap:
-------------------

Syntax: monitorcap:<vmin>;<vmax>;<hmin>;<hmax>

This describes the capabilities of a multisync monitor. Don't use it
with a fixed-frequency monitor! For now, only the Falcon frame buffer
uses the settings of "monitorcap:".

  <vmin> and <vmax> are the minimum and maximum, resp., vertical frequencies
your monitor can work with, in Hz. <hmin> and <hmax> are the same for
the horizontal frequency, in kHz.

  The defaults are 58;62;31;32 (VGA compatible).

  The defaults for TV/SC1224/SC1435 cover both PAL and NTSC standards.

4.1.9) keep
------------

If this option is given, the framebuffer device doesn't do any video
mode calculations and settings on its own. The only Atari fb device
that does this currently is the Falcon.

  What you reach with this: Settings for unknown video extensions
aren't overridden by the driver, so you can still use the mode found
when booting, when the driver doesn't know to set this mode itself.
But this also means, that you can't switch video modes anymore...

  An example where you may want to use "keep" is the ScreenBlaster for
the Falcon.


4.2) atamouse=
--------------

Syntax: atamouse=<x-threshold>,[<y-threshold>]

  With this option, you can set the mouse movement reporting threshold.
This is the number of pixels of mouse movement that have to accumulate
before the IKBD sends a new mouse packet to the kernel. Higher values
reduce the mouse interrupt load and thus reduce the chance of keyboard
overruns. Lower values give a slightly faster mouse responses and
slightly better mouse tracking.

  You can set the threshold in x and y separately, but usually this is
of little practical use. If there's just one number in the option, it
is used for both dimensions. The default value is 2 for both
thresholds.


4.3) ataflop=
-------------

Syntax: ataflop=<drive type>[,<trackbuffering>[,<steprateA>[,<steprateB>]]]

   The drive type may be 0, 1, or 2, for DD, HD, and ED, resp. This
   setting affects how many buffers are reserved and which formats are
   probed (see also below). The default is 1 (HD). Only one drive type
   can be selected. If you have two disk drives, select the "better"
   type.

   The second parameter <trackbuffer> tells the kernel whether to use
   track buffering (1) or not (0). The default is machine-dependent:
   no for the Medusa and yes for all others.

   With the two following parameters, you can change the default
   steprate used for drive A and B, resp. 


4.4) atascsi=
-------------

Syntax: atascsi=<can_queue>[,<cmd_per_lun>[,<scat-gat>[,<host-id>[,<tagged>]]]]

  This option sets some parameters for the Atari native SCSI driver.
Generally, any number of arguments can be omitted from the end. And
for each of the numbers, a negative value means "use default". The
defaults depend on whether TT-style or Falcon-style SCSI is used.
Below, defaults are noted as n/m, where the first value refers to
TT-SCSI and the latter to Falcon-SCSI. If an illegal value is given
for one parameter, an error message is printed and that one setting is
ignored (others aren't affected).

  <can_queue>:
    This is the maximum number of SCSI commands queued internally to the
    Atari SCSI driver. A value of 1 effectively turns off the driver
    internal multitasking (if it causes problems). Legal values are >=
    1. <can_queue> can be as high as you like, but values greater than
    <cmd_per_lun> times the number of SCSI targets (LUNs) you have
    don't make sense. Default: 16/8.

  <cmd_per_lun>:
    Maximum number of SCSI commands issued to the driver for one
    logical unit (LUN, usually one SCSI target). Legal values start
    from 1. If tagged queuing (see below) is not used, values greater
    than 2 don't make sense, but waste memory. Otherwise, the maximum
    is the number of command tags available to the driver (currently
    32). Default: 8/1. (Note: Values > 1 seem to cause problems on a
    Falcon, cause not yet known.)

      The <cmd_per_lun> value at a great part determines the amount of
    memory SCSI reserves for itself. The formula is rather
    complicated, but I can give you some hints:
      no scatter-gather  : cmd_per_lun * 232 bytes
      full scatter-gather: cmd_per_lun * approx. 17 Kbytes

  <scat-gat>:
    Size of the scatter-gather table, i.e. the number of requests
    consecutive on the disk that can be merged into one SCSI command.
    Legal values are between 0 and 255. Default: 255/0. Note: This
    value is forced to 0 on a Falcon, since scatter-gather isn't
    possible with the ST-DMA. Not using scatter-gather hurts
    performance significantly.

  <host-id>:
    The SCSI ID to be used by the initiator (your Atari). This is
    usually 7, the highest possible ID. Every ID on the SCSI bus must
    be unique. Default: determined at run time: If the NV-RAM checksum
    is valid, and bit 7 in byte 30 of the NV-RAM is set, the lower 3
    bits of this byte are used as the host ID. (This method is defined
    by Atari and also used by some TOS HD drivers.) If the above
    isn't given, the default ID is 7. (both, TT and Falcon).

  <tagged>:
    0 means turn off tagged queuing support, all other values > 0 mean
    use tagged queuing for targets that support it. Default: currently
    off, but this may change when tagged queuing handling has been
    proved to be reliable.

    Tagged queuing means that more than one command can be issued to
    one LUN, and the SCSI device itself orders the requests so they
    can be performed in optimal order. Not all SCSI devices support
    tagged queuing (:-().

4.6 switches=
-------------

Syntax: switches=<list of switches>

  With this option you can switch some hardware lines that are often
used to enable/disable certain hardware extensions. Examples are
OverScan, overclocking, ...

  The <list of switches> is a comma-separated list of the following
items:

  ikbd: set RTS of the keyboard ACIA high
  midi: set RTS of the MIDI ACIA high
  snd6: set bit 6 of the PSG port A
  snd7: set bit 6 of the PSG port A