Bochs VBE Extensions: Difference between revisions
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=== Clearing display memory === |
=== Clearing display memory === |
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When enabling the VBE extensions, Bochs clears the video memory (i.e. sets all bytes to 0). To prevent this from happening, use the VBE_DISPI_NOCLEARMEM flag (0x80) when enabling the VBE extensions (so write a value of VBE_DISPI_ENABLED | VBE_DISPI_NOCLEARMEM (0x81) for banked mode and VBE_DISPI_ENABLED | VBE_DISPI_LFB_ENABLED | VBE_DISPI_NOCLEARMEM (0xC1) for LFB). |
When enabling the VBE extensions, Bochs clears the video memory (i.e. sets all bytes to 0). To prevent this from happening, use the VBE_DISPI_NOCLEARMEM flag (0x80) when enabling the VBE extensions (so write a value of VBE_DISPI_ENABLED | VBE_DISPI_NOCLEARMEM (0x81) for banked mode and VBE_DISPI_ENABLED | VBE_DISPI_LFB_ENABLED | VBE_DISPI_NOCLEARMEM (0xC1) for LFB). |
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=== Finding out capabilities === |
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Based on source code examination for Bochs (iodev/vga.cc) setting VBE_DISPI_GETCAPS in VBE_DISPI_INDEX_ENABLE makes the VBE_DISPI_INDEX_ (XRES / YRES / BPP) fields return their maximum values when read instead of the current values. |
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=== Miscellaneous === |
=== Miscellaneous === |
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[TODO: check and describe VBE_DISPI_INDEX_VIRT_WIDTH/HEIGHT, VBE_DISPI_INDEX_X/Y_OFFSET |
[TODO: check and describe VBE_DISPI_INDEX_VIRT_WIDTH/HEIGHT, VBE_DISPI_INDEX_X/Y_OFFSET, VBE_DISPI_8BIT_DAC] |
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=== Example code === |
=== Example code === |
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