OSBYTE &73

OSBYTE &73 (115) - Select shadow RAM bank used

   On entry:
       X=0 Shadow bank 8
       X=1 Shadow bank 9
   
   Electron OS:
   Blank/restore palette
   On entry:
       X=0  restores the palette, on exit X=0
       X<>0 sets the whole palette to black if in high resolution mode
            on exit, X<4
   

Software using NMIs in high resolution screen modes can prevent snow appearing on the screen during NMIs (due to ULA reuse) by blanking the palette.

See also

• OSBYTE &49 - Check for Integra-B shadow memory
• OSBYTE &6C - Select Master/Integra-B shadow memory
• OSBYTE &6F - Select BBC B shadow memory
• OSBYTE &70 - Select memory for Master VDU access
• OSBYTE &71 - Select memory for Master video display
• OSBYTE &72 - Select future use of shadow memory
• OSBYTE &73 - Select shadow bank
• OSBYTE &74 - Check for Solidisk shadow memory
• Paging in video memory
• http://mdfs.net/Docs/Comp/BBC/Osbyte00

Jgharston 21:52, 26 May 2009 (UTC) Jgharston (talk) 20:32, 3 April 2015 (UTC)