Difference between revisions of "Flash ROM"
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| − | The Flash is a 256 kiB or 1 MiB non-volatile <abbr title="Thin Small Outline Package">TSOP</abbr> ROM chip and connected to the [[MCPX]] via the <abbr title="Low Pin Count">LPC</abbr> bus. | + | The Flash is a 256 kiB or 1 MiB [[Wikipedia:Flash_memory|non-volatile <abbr title="Thin Small Outline Package">TSOP</abbr> ROM chip]] and connected to the [[MCPX]] via a parallel bus on [[hardware revisions]] 1.0 to 1.4. The 256 kiB ROM on revision 1.6 is stored in the Xcalibur chip, not a flash chip, and is connected to the [[MCPX]] via the [[Wikipedia:Low Pin Count|<abbr title="Low Pin Count">LPC</abbr>]] bus (Xbox revision 1.6). |
| − | The Flash ROM is mapped at | + | The Flash ROM is mapped at physical addresses 0xFF000000 to 0xFFFFFFFF (revision 1.0) or 0xFFFFFDFF (revisions 1.1 - 1.6). The 256 kiB or 1 MiB ROM is [[Wikipedia:Aliasing (computing)#Hardware aliasing|aliased]] throughout this 16 MiB address range. |
| + | The ROM is commonly based in software at either 0xFFF00000 or 0xFFFC0000 as these are the addresses of the last alias for 1 MiB and 256 kiB respectively. | ||
| + | Due to [[Exploits#MIST hack|the MIST hack]], Microsoft blocked the use of flash ROM in the range of the [[MCPX ROM]] (0xFFFFFE00 - 0xFFFFFFFF) for revisions 1.1 to 1.6. Once the MCPX ROM is hidden, accessing this memory range will freeze the system. | ||
For the content of the Microsoft flash images see [[BIOS]]. | For the content of the Microsoft flash images see [[BIOS]]. | ||
Latest revision as of 04:43, 21 February 2024
The Flash is a 256 kiB or 1 MiB non-volatile TSOP ROM chip and connected to the MCPX via a parallel bus on hardware revisions 1.0 to 1.4. The 256 kiB ROM on revision 1.6 is stored in the Xcalibur chip, not a flash chip, and is connected to the MCPX via the LPC bus (Xbox revision 1.6).
The Flash ROM is mapped at physical addresses 0xFF000000 to 0xFFFFFFFF (revision 1.0) or 0xFFFFFDFF (revisions 1.1 - 1.6). The 256 kiB or 1 MiB ROM is aliased throughout this 16 MiB address range. The ROM is commonly based in software at either 0xFFF00000 or 0xFFFC0000 as these are the addresses of the last alias for 1 MiB and 256 kiB respectively. Due to the MIST hack, Microsoft blocked the use of flash ROM in the range of the MCPX ROM (0xFFFFFE00 - 0xFFFFFFFF) for revisions 1.1 to 1.6. Once the MCPX ROM is hidden, accessing this memory range will freeze the system.
For the content of the Microsoft flash images see BIOS.
