Notes - Updated TODO and added notes on structure of vbox graphics

[tpg/acess2.git] / Notes / VBox_VGA.txt

diff --git a/Notes/VBox_VGA.txt b/Notes/VBox_VGA.txt
new file mode 100644 (file)
index 0000000..3634fb8
--- /dev/null
+++ b/Notes/VBox_VGA.txt
@@ -0,0 +1,19 @@
+VirtualBox BochsGA->VGA Translation (From DevVGA.cpp)
+- Assuming non 4bpp mode
+
+GR[0x06].3,2,0 = 0,1,1                 Miscellaneous Graphics Register Mem Map = 64K@A0000, AlphaNum Disable)
+CR[0x17].1,0 = 1,1                     CRTC Mode Control Register      MAP14,MAP13
+CR[0x13] = vbe_line_offset / 8         Offset Register         (aka Pitch)
+CR[0x01] = virtual_width / 8 - 1       End Horizontal Display Register
+CR[0x12] = height                      Virtical Display End Register
+CR[0x07].6,2 = height >> 8             Overflow Register [VDE9,VDE8]
+CR[0x18] = 0xFF                                Line Compare Register
+CR[0x07].4 = 1                         Overflow Register [LC8]
+CR[0x09].6 = 1                         Maximum Scan Line Register [LC9]
+
+SR[4].3 = 1                            Sequencer Memory Mode   Chain 4 Enable
+SR[2].3,2,1,0 = 1,1,1,1                        Map Mask Register       All planes enabled
+SR[7].0 = 1                            NON-VGA
+
+GR[0x05].6-5 = 2                       Graphics Mode Register  256 color shift mode
+CR[0x09].7,4-0 = 0,0                   Maximum Scan Line Register [SD=0,MSL=0]