Figure 5 RAM access in normal and shadow modes In normal mode the RAM can be thought of as 44K from address &0000- &AFFF. The top 12K of this RAM from address &8000-&AFFF is paged into the memory map when required in place of the bottom 12K of the sideways ROM space, see 5.4.2. The remaining 20K of RAM is set aside for the shadow screen memory, while it always exists, it is not available to the system in normal mode. The bank of 44K RAM we shall call "normal RAM". In normal mode, VDUSEL (IC36 pin 17) is always zero. Any code executing anywhere within normal RAM in normal mode will always access normal RAM, it cannot access shadow RAM. 17