MODE 4

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Starship Command (Acornsoft, 1983)
Vortex (Software Invasion, 1983)
Tomcat (Players, 1989)

MODE 4 is a medium-resolution screen MODE, introduced on the BBC Micro Model A and supported by the entire BBC series including the Archimedes. It allows detailed graphics to be shown while leaving 15 KB or more free for programs; however to achieve this the display is made monochrome.

In Elite and Revs a custom interrupt routine splits the screen in two; the top half is configured as MODE 4 to show the exterior view in detail.

MODE 4
Type Graphical ('ASCII')
Resolution Text 40 × 32 characters
Graphics 320 × 256 pixels
Character size 8 × 8 pixels, user definable
Pixel aspect 1:1 (square)
Bits per pixel 1
Default palette Logical colour Actual colour
0 0 (black)
1 7 (white)
Memory allocated 10240 bytes
on screen 10240 bytes
Address range Model B etc. &5800..&7FFF
Configuration Video ULA control register &88
Video ULA palette register file &07 &17 &27 &37 &47 &57 &67 &77
&80 &90 &A0 &B0 &C0 &D0 &E0 &F0
CRTC register file &3F &28 &31 &24 &26 &00
&20 &22 &01 &07 &67 &08
(from table in MOS 1.20 at &C486..&C491)
Screen display MODEs

MODE 0 | MODE 1 | MODE 2 | MODE 3 | MODE 4 | MODE 5 | MODE 6 | MODE 7
MODE 8 | MODE 9 | MODE 10 | MODE 11 | MODE 12 | MODE 13 | MODE 14
MODE &60 | MODE &61 | MODE &62 | MODE &63 | MODE &64 | MODE &65 | MODE &66 | MODE &67
MODE &68 | MODE &69 | MODE &6A | MODE &6B | MODE &6C | MODE &6D | MODE &6E | MODE &6F
MODE | VDU 22

-- beardo 14:13, 16 September 2006 (BST)