Understanding video adapter resolutions

[GordonVCD]

I am buying a new monitor for temporary use with an old Win XP computer (a newer computer will eventually be purchased), and want to be sure that, whatever monitor I purchase, will work with the current computer's video adapter. The current adapter is an Intel 82845g on the motherboard. The MB also has an unused AGP 4x slot. I tried the computer with one of my existing 1680x1050 monitors and it seemed to be fine. The display didn't appear to be stretched in any way. However, I can't understand why the video adapter supports 1680x1050, which was showing on the display settings, when the monitor was attached. If I go to Advanced on the Settings menu and then list "All Modes", 1680x1050 doesn't show up or even some scaled version of it (I thought that this listing would show all the resolutions of which the adapter and the associated driver are capable). Does anyone know why 1680x1050 doesn't show? I can't imagine that the monitor makes the adjustment because 1680x1050 shows on the Display Settings resolution "slider".

I am interested in all this, because most monitors are now 1920x1080 and, if I buy one of these, I don't want to find that the video adapter can't support it, especially as there may be a restocking charge. Given that there is an AGP slot, it may be possible to find a cheap AGP card that would support 1920x1080 (probably for ~$40), though this could be difficult as there aren't too many AGP cards around these days.

In this transitional situation, the monitor will only be used to display textual information, not heavy duty video stuff.

Thank you

GordonVCD

[jagabo]

I think what you're saying is that 1680x1050 doesn't show up in your display settings unless a 1680x1050 monitor is attached. That's because the display settings won't show you resolutions above what the currently attached monitor supports. You should just look up what maximum resolution the graphics chipset supports.

ftp://download.intel.com/design/chipsets/datashts/29074602.pdf

The 82845 data sheet talks of analog resolutions up to 2048x1536 at 60 Hz and 1920x1080 at up to 85 Hz. Some features may not work at that resolution though: 3D graphics (Win 7 and Vista may not be able to use Aero) and video overlay show lower limits.

One other possible problem if you're using VGA: some monitors can't display VGA signals at their native resolution. I have an old LCD monitor that has a native resolution of 1680x1050 and accepts that via DVI. But the VGA input only accepts up to 1280x1024.

[MJA]

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[GordonVCD]

I am trying to get the title fixed, but I don't seem to be able to change it through "Edit".

[GordonVCD]

Thank you, jagabo. The correct resolution does show up in Settings (where the slider is), but it isn't listed in Settings/Advanced/All Modes, which I thought should show all achievable resolutions.

The data sheet is useful and encoraging, but I don't really understand the details. It talks about achieving a resolution of 1920x1080, but in "Dual-Channel Mode". I am guessing that the availability of this depends on how the chip-set was designed into the specific video adapter.

GordonVCD

[jagabo]

A google search does show that a lot of people with 8245g graphics can't get 1920x1080 out of them.

[GordonVCD]

Yes you are right, there are quite a few questions about this that one can see with Google.

However, I made a mistake when checking out the possible resolutions of this adapter. I forgot to uncheck "Hide modes that this monitor cannot display". Having unchecked this, the adapter shows additional modes which include 1920x1080 in 256 colors/High color/True Color at 60/75/85/100Hz. However, surprisingly (to me) 1680x1050 is absent from this expanded list. This puzzles me because I tested a 1680x1050 monitor with this computer, it worked fine, and 1680x1050 showed up on the Settings slider. Does anyone know why 1680x1050 would show up on the Settings slider if it doesn't show up on the expanded list when the "Hide" box has been unchecked?

I obviously don't understand how video adapters work yet and show their information!

Thank you
GordonVCD

[GordonVCD]

Referring back to my initial question in this thread, I did eventually purchase a new 1680x1050 for this old machine, and it worked fine. No sign of 1680x1050 in the list of modes (including hidden), but the Dispay Settings showed that 1680x1050 was available on the settings slider, as soon as the monitor was attached.

GordonVCD