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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 [2017/07/25 16:15] 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. | ||
| - | The ROM $00 machines may be upgraded to use a 32K ROM via a pair of solder/trace jumpers on the board. | + | 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. |
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| + | The ROM $00 machines may be upgraded to use a 32K ROM via a pair of solder/butterfly 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. | ||