Thanks--and Help!

ME dugan at
Tue Feb 22 11:06:04 PST 2000

Some educated guesses to answers listed below:

On Tue, 22 Feb 2000, Bonnie Allen wrote:
> Subject: Thanks--and Help!
> I'm having a problem I can't seem to resolve: I can't read the terminal
> windows. No matter what color schema I select, the screen appears in the
> font color, with a tiny line of the background color around it. I can type
> something and it's there, but I can't see it. If I type something, and then
> change the color schema in Gnome, I can see what I've already typed, but it
> disappears if I try to change it or add to it.

Guesses start here:

Older Video cards have limited memory. Gnome is a color palette hungry
window manager. When all of the colors of your palette are consumed by
system icons, desktop images, and backgrounds, this leaves very little in
the way for colors for other applications, including X-terms.

Gnome works better in 24, or 16 bit color depth. 8 bit color depth only
affords about 256 colors, while 16 bit affords about 65 thousand, and 24
bit allows for about 16 million:
(2^8=256, 2^16=65536, 2^24=16777216)

If you have 1 Mb of video RAM or less, you may not have a palette of more
than 256 colors at 1024x768.

There is a quick calculation you can perform to find out how many colors
your video card may display at each resolution:

(Horizontal screen size in pixels) x (vertical screen size in pixels) x
(Number of bits for colors divided by 8)

If you have 640x480 @ 24 bit colors depth:
640 x 480 x (24 bits/ 8 (bits/byte)) = 921600 bytes required.
(Note this is almost 1 Mb.)

If you have 1024x768 @ 24 bit color depth:
1024 x 768 x (24 bits / 8 (bits/byte)) = 2359296 bytes required.

If your video card has only 512 K of RAM, and you try to set 24 bit color
depth with 640x480, XFree86 is likely to give you errors. If it does not
error out, but allows the settings, you may end up with video corruption
on your screen, or the non-assignment of new colors from your palette to
work in the window. 

The reason for the above is you are trying to us 921 K of RAM on a card
which only has 512K of RAM.

The video corruption may occur if the RAM on the video card is set for
wrapped use when the max memory address is exceeded. (When you try to
write to the memory address , one address higher than 512 K of RAM,
assuming this is the size of memory on your card.

RAM on the video card no only limits the number of colors in your palette,
but also the maximum resolutions. A trade-off exists for resolution and
number of colors. (Some cards may allow for 16 colors, which is just a
4-bit color depth. I am certain the default Gnome desktop would hate only
having 16 colors!)

> Everything else looks fine, except that I also can't get Linux to accept
> anything but a 640 X 480 resolution for my monitor. At least, I'm assuming
> that's the case, since I can't see the whole desktop without dragging stuff
> around on it. And it won't accept the sync rates recommended in the
> monitor's manual.

Do you have a VGA adapter, or SVGA adapter? How many pins does the video
connector from your monitor have? Only 9? 14-16 pins?

Older monitors may only be able to display @ 640x480.

Older Graphics cards may only be able to signal for 640x480 as max
resolution also.

So some questions beyond the ones above:
Is your video card old?
How much RAM does it have?
It your monitor old?
Have you been able to use higher resolutions when in other OS, like

What X Server are you using? VGA 16? S3? SVGA?

And then, is your X Server configured to run at 8 bit color depth instead
of 16, or 24? (Even if you have a new card, if the X server is configured
to run at 8 bit color depth, then only around 256 colors exist for the
palette in display. Your problem may be as simple as configuring X to use
a larger color depth if all of your equipment is newer, and you have
plenty of RAM and the proper X Server for your equipment.

> Is this a video card problem? I also can't find any reference to my video
> card in my Windows control panel, where Bill McCarty suggests you look
> (Learning Red Hat Linux). So I don't know if it's configured right.

It could be a video card problem, a video server problem (wrong one choice
for your card), memory limitation, or any of the problems listed above.
The easiest solution would be an XF86.Config setting change if it is just a
mis-configuration issue.

There is another possible solution:
There is something that may need to be configured differently in GNOME. I
have not used GNOME much. I am stuck in FVWM, and FVWM-2 land. (Old
habits die hard.) A number of people here use Gnome regularly, and may
have a suggestion from the window manager of something to try...

> I'd appreciate any suggestions anyone might have. I'm sorry to say they
> will probably have to be couched in near dummies-level language for me to
> understand them!

If you do not understand any of the items described above, let us know and
we can try to find better language to describe them.


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