The OS, BASIC and AMSDOS are based on CPC6128 ROMs and have all been patched.
=== OS patches ===
The OS ROM has been patched in the following way:
* Offset &67D has changed from:
call &0723
call &06fc
ld hl,&0688
jr (?)
to:
call &b900 ;; enable upper rom
ld bc,&df07 ;; select upper rom (7 - normally DOS/AMSDOS)
out (c),c
jp &dc03 ;; call into DOS/AMSDOS rom
* Offset: &1052 and &1053 which define the first 2 colours of the "1st" palette have been changed from &04 to &14. The "1st" and "2nd" palette are swapped between in BASIC to implement flashing colours. &04 is blue. &14 is black.
* Offset: &1063 and &1064 which define the first 2 colours of the palette "2nd" palette have been changed from &04 to &14. The "1st" and "2nd" palette are swapped between in BASIC to implement flashing colours. &04 is blue, &14 is black.
When the OS starts, the colours are set to black and code patched into the DOS/AMSDOS rom is executed.
=== BASIC patches ===
The BASIC ROM has been patched in the following way:
* Offset &33 has been set to 0. It is the first character of " BASIC 1.1" text.
scf
ret
When BASIC is started the sign on messages are not displayed, and it auto runs a command-line.