OSBYTE &70

OSBYTE &70 (112) - Select Main/Shadow for VDU access

   On entry:
       X=0 Use whatever memory the current screen MODE uses
       X=1 Use main memory
       X=2 Use shadow memory
   On exit:
       X=preserved
   RISC OS:
   The value of X can be greater than 2 as well, and instructs the VDU
   drivers to use the bank at screenbase+(X*modesize)

This call specifies which bank of memory the Master VDU drivers access. Using this and OSBYTE &71 a program can use the VDU to write to one bank of memory while the other is being displayed.

The setting is stored in the OSBYTE &F0 variable.

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 (talk) 01:11, 4 April 2015 (UTC)