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flat assembler > OS Construction > Video memory

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l4m2



Joined: 15 Jan 2015
Posts: 613
When I use DEBUG int 10/4F00 to see the info, it says I have 4095*64KB=255.9375MB memory to use, and the windows info also give 260MB address(Exxxxxxx, F7(8-B)xxxxx).
What do the rest of the video memory do? Is it unaccessable?
Post 11 Dec 2017, 01:08
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 15913
Location: SDSS J140821.67+025733.2
You can probably use for scrolling. Just change the start offset from the default of zero and now you can see other parts of the memory on the screen.
Post 11 Dec 2017, 01:14
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l4m2



Joined: 15 Jan 2015
Posts: 613
I guess scrolling uses the 256MB is enough, but my vm is 1GB
Post 11 Dec 2017, 05:50
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 15913
Location: SDSS J140821.67+025733.2
I suspect the OS is supposed to have the necessary driver to properly configure the video card for the desired purpose and use all the features. It is not the job of the BIOS to do that. The BIOS gives you enough to get things up, but further than that you'll need to do yourself.
Post 11 Dec 2017, 05:57
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cod3b453



Joined: 25 Aug 2004
Posts: 620
The Ex..x range will be just the VRAM and the Fx..x ranges tend to be expansion ROM areas (there are also the legacy address ranges and possibly others related to ACPI). It is possible to obtain [more] exact information by enumerating the PCI bus.
Post 17 Feb 2018, 00:38
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