Re: Boot Logo Questions....

Riley Williams (
Fri, 15 May 1998 02:55:54 +0100 (BST)

Hi Pat.

> I'd prefer this order since there are going to be the unforseen
> times when the card may be capable of it but the monitor isn't. If
> we default to plain vanilla text mode and do everything else as an
> option, the suprises will be minimised.

If you don't mind my pointing it out, any monitor that can be
connected to a STANDARD VGA adapter can display ALL of those modes,
and any that can't will only get modes it can display selected by the
stated algorithm, so there's no possibility of 'unforseen times', as
you put it...

>> 1. Can the video card support 640x480x16M? If so, use it.
>> 2. Can the video card support 640x480x64K? If so, use it.
>> 3. Can the video card support 640x480x256? If so, use it.
>> 4. Can the video card support 320x200x256? If so, use it.
>> 5. Can the video card support 640x480x16? If so, use it.
>> 6. Can the video card support 320x200x16? If so, use it.
>> 7. Does the card support graphics? If so, use the lowest mode it
>> supports.
>> 8. Use a text only mode.

Standard VGA supports a resolution of 640x480, so any VGA or SVGA
monitor MUST be able to support that resolution by design. Since VGA
and SVGA are ANALOGUE standards, the colourdepth is irrelevant as far
as the monitor is concerned, all they will see is a voltage varying
between the same limits on each of the RGB guns, and the fact that the
steps vary in size is of no interest to the monitor.

The above only leaves systems with no VGA modes supported to be
analysed, so let's do so:

A. CGA - This is a digital mode, supporting either 320x200x4 colours
or 640x200x2 colours. Since neither of these are in the scan list,
option 7 would apply, and the 320x200x4 mode would be selected.

B. EGA - This is a digital mode, supporting a resolution of either
640x350x16 or 640x200x16. Either CGA or EGA monitors could be
connected to an EGA adapter, but the CGA monitors do not support
the 640x350 mode, so it has NOT been included in the scan list.
For this reason, a system with an EGA adapter would select option
5 from the above table.

C. Amstrad's version of CGA, available in their PC1512, PC1640 and
PC2x86 computers, supported 320x200x16 colours in an EGA fashion,
but did NOT support the EGA standard 640x200x16 colours. This is
the ONLY case where option 6 is likely to be selected, and only
the Amstrad PC2386 is capable of running Linux since all the other
members of this group had sub-386 processors.

D. Hercules MonoGraphics - This is a digital mode, but only supports
two colours. Since there is only one graphics mode on these cards,
720x348x2, option 7 would result in that mode being selected.

E. MDA - This is a text only adapter, so option 8 would apply.

F. Other specialist cards. In each case, either option 7 or option 8
would apply, resulting in a mode compatible with all monitors that
could be connected to the card.

Hopefully this helps...

Best wishes from Riley.

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