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mg_notes:apple_iic:firmware_bank_switch [2017/07/17 15:55]
M.G.
mg_notes:apple_iic:firmware_bank_switch [2017/07/17 15:56]
M.G.
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 All Apple %%//%%c and IIc Plus computers //except ROM $00// ship with two 16K firmware banks, each visible from $C100-$FFFF. ​ The visible bank is switched by a write to $C028. ​ This is not well-documented by the Apple documentation. All Apple %%//%%c and IIc Plus computers //except ROM $00// ship with two 16K firmware banks, each visible from $C100-$FFFF. ​ The visible bank is switched by a write to $C028. ​ This is not well-documented by the Apple documentation.
 +
 +It is not possible to know which firmware bank is active except by reading locations in the firmware, there is no status bit available in the I/O space.
  
 The ROM $00 machines may be upgraded to use a 32K ROM via a pair of solder/​trace jumpers on the board. The ROM $00 machines may be upgraded to use a 32K ROM via a pair of solder/​trace jumpers on the board.
  
 The aux bank mostly contains firmware supporting the features not present or less mature in the original Apple %%//%%c: 3.5%%"​%% drive/​SmartPort,​ serial and keyboard buffering, memory expansion card, diagnostics,​ and (for the Plus) accelerator. The aux bank mostly contains firmware supporting the features not present or less mature in the original Apple %%//%%c: 3.5%%"​%% drive/​SmartPort,​ serial and keyboard buffering, memory expansion card, diagnostics,​ and (for the Plus) accelerator.