MODE 0 is a high-resolution screen MODE, introduced on the BBC Micro Model B and supported by the entire BBC series including the Archimedes. It allows 80 columns of text to be shown but leaves only 9 KB for programs -- even less if a disc interface or Econet is fitted.
MODEs 0 and 3 are the only MODEs to offer 80 text columns. These allow the BBC Micro to work competently as a terminal to mainframes, bulletin boards and the like. Since this was a key requirement in the BBC's specification for a Computer Literacy machine, Acorn developers are said to have worked overnight to get MODE 0 working on the Proton before its demonstration to BBC executives.
As with MODE 3, the bandwidth (pixel rate) is 16 MHz -- too high for the televisions of the day. Characters are recognisable at close range, thanks to Acorn's carefully designed character set, but a monitor is required buying for prolonged use. Compounded by the unusual tall pixels and large memory footprint for a monochrome display, few games have adopted MODE 0 and so it is used mostly for business applications -- word processors and spreadsheets.
|Resolution||Text||80 × 32 characters|
|Graphics||640 × 256 pixels|
|Character size||8 × 8 pixels, user definable|
|Pixel aspect||1:2 (tall)|
|Bits per pixel||1|
|Default palette||Logical colour||Actual colour|
|on screen||20480 bytes|
|Address range||Model B etc.||&3000..&7FFF|
|Configuration||Video ULA control register||&9C|
|Video ULA palette register file|| &07 &17 &27 &37|
&47 &57 &67 &77
&80 &90 &A0 &B0
&C0 &D0 &E0 &F0
|CRTC register file|| &7F &50 &62 &28|
&26 &00 &20 &22
&01 &07 &67 &08
(from table in MOS 1.20 at &C46E..&C479)
|Screen display MODEs|
MODE 0 | MODE 1 | MODE 2 | MODE 3 | MODE 4 | MODE 5 | MODE 6 | MODE 7
-- beardo 14:09, 16 September 2006 (BST)