OSBYTE &6C

OSBYTE &6C (108) - Main/Shadow RAM access

   On entry:
       X=0  Main memory appears from &3000 to &7FFF
       X<>0 Shadow memory appears from &3000 to &7FFF
   On exit:
       X    preserved

This has immediate effect and allows the user to access the Master shadow RAM, for instance, to load or save it or manipulate it directly. The memory that is accessed by the Master VDU drivers and displayed can set with OSBYTE &70 and OSBYTE &71.

Shadow RAM on the BBC B with the Integra-B system is also paged in with OSBYTE &6C. The Aries and Watford systems use OSBYTE &6F.

On the BBC B+ the displayed memory is always the bank selected with MODE or OSBYTE &72, and the user can only access the shadow memory by calling OSRDSC.

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) 01:10, 4 April 2015 (UTC)