Date   : Wed, 22 Sep 2010 07:58:43 +0100
From   : adsb@... (Andrew Benham)
Subject: 32K Message

On 22/09/10 03:36, Rick Murray wrote:

>  From the annotated OS disassembly:
> --8<--------
>   DB67    AND     &0267   ;if A=&FE and bit 7 of 0267 is set then continue
>   DB6A    BPL     &DB87   ;else ignore start up message
>   DB6C    LDY     #&02    ;output to screen
>   DB6E    JSR     &DEA9   ;'BBC Computer ' message
>   DB71    LDA     &028D   ;0=warm reset, anything else continue
>   DB74    BEQ     &DB82   ;
>   DB76    LDY     #&16    ;by checking length of RAM
>   DB78    BIT     &028E   ;
>   DB7B    BMI     &DB7F   ;and either
>   DB7D    LDY     #&11    ;
>   DB7F    JSR     &DEA9   ;finishing message with '16k' or '32k'
>   DB82    LDY     #&1B    ;and two newlines
>   DB84    JSR     &DEA9   ;
> --8<--------

The '16k' and '32k' messages also include a bell character (0x07)
which is why one gets a beep on a hard reset.

-- 
Andrew Benham     Southgate, London N14, United Kingdom

The gates in my computer are AND OR and NOT, not "Bill"