NAND Memory Layout: Difference between revisions
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The TI-Nspire OS advertises 27.8MB of what it calls "storage capacity", which is the flash memory which can be filled with TI-Nspire documents. Saved documents are always stored in the storage memory. Documents being edited probably have a working copy in RAM, copied to the storage memory when the document is saved. In the 4300.8KB left, we find the OS image (3020KB for the .tno), and perhaps certificates, part of the boot code which wouldn't be stored in the [[Hardware#Boot.2FKernel.28.3F.29_memory|NOR flash]] (although 512KB seems more than enough for a boot code), and more... | The TI-Nspire OS advertises 27.8MB of what it calls "storage capacity", which is the flash memory which can be filled with TI-Nspire documents. Saved documents are always stored in the storage memory. Documents being edited probably have a working copy in RAM, copied to the storage memory when the document is saved. In the 4300.8KB left, we find the OS image (3020KB for the .tno), and perhaps certificates, part of the boot code which wouldn't be stored in the [[Hardware#Boot.2FKernel.28.3F.29_memory|NOR flash]] (although 512KB seems more than enough for a boot code), and more... | ||
The ''Handheld Status'' dialog shows 5.7MB of "spaced used" after a reset. The document tree only contains the document "Getting started" after a reset. The space used for the system contains at least the | The ''Handheld Status'' dialog shows 5.7MB of "spaced used" after a reset. The document tree only contains the document "Getting started" after a reset. The space used for the system contains at least the 1.57MB of archive memory for the TI-84 Plus emulation, or even the whole ROM image (certificates, boot code, OS code and archive memory, 2MB). We are not sure about the remaining 4.13MB/3.7MB. It is clear that the archive memory of the TI-84 Plus is stored in flash memory and not in RAM because it survives a keypad swap. | ||
Since 32MB of RAM is available, which is quite a lot, we think the whole OS code is decrypted from the [[OS_upgrade_files#TI-Nspire.img|OS image]] and copied to RAM at boot time, when the message "Loading Operating System..." is displayed during ~8 seconds. The RAM is also used as temporary storage transparently for the user as described above. The [[OS_upgrade_files#Compressed_file_system|file system]] compressed in the OS image may also be uncompressed to RAM at boot time when the message "Preparing file system, please wait..." is displayed during ~2 seconds to setup the OS file system. Since 2 seconds is quite fast, only part of the compressed files may be uncompressed (for example only the needed locale). For information the whole compressed file system (including the TI-84 Plus archive memory) is 2363.4KB once uncompressed. | Since 32MB of RAM is available, which is quite a lot, we think the whole OS code is decrypted from the [[OS_upgrade_files#TI-Nspire.img|OS image]] and copied to RAM at boot time, when the message "Loading Operating System..." is displayed during ~8 seconds. The RAM is also used as temporary storage transparently for the user as described above. The [[OS_upgrade_files#Compressed_file_system|file system]] compressed in the OS image may also be uncompressed to RAM at boot time when the message "Preparing file system, please wait..." is displayed during ~2 seconds to setup the OS file system. Since 2 seconds is quite fast, only part of the compressed files may be uncompressed (for example only the needed locale). For information the whole compressed file system (including the TI-84 Plus archive memory) is 2363.4KB once uncompressed. | ||
Revision as of 13:15, 5 August 2007
32MB are available in the flash memory used for storage. As in other TI calculator models with flash memory, it is used to store both the Operating System and what was called the "archive memory" on the previous models (this term loses its sense with the TI-Nspire as we'll see).
The TI-Nspire OS advertises 27.8MB of what it calls "storage capacity", which is the flash memory which can be filled with TI-Nspire documents. Saved documents are always stored in the storage memory. Documents being edited probably have a working copy in RAM, copied to the storage memory when the document is saved. In the 4300.8KB left, we find the OS image (3020KB for the .tno), and perhaps certificates, part of the boot code which wouldn't be stored in the NOR flash (although 512KB seems more than enough for a boot code), and more...
The Handheld Status dialog shows 5.7MB of "spaced used" after a reset. The document tree only contains the document "Getting started" after a reset. The space used for the system contains at least the 1.57MB of archive memory for the TI-84 Plus emulation, or even the whole ROM image (certificates, boot code, OS code and archive memory, 2MB). We are not sure about the remaining 4.13MB/3.7MB. It is clear that the archive memory of the TI-84 Plus is stored in flash memory and not in RAM because it survives a keypad swap.
Since 32MB of RAM is available, which is quite a lot, we think the whole OS code is decrypted from the OS image and copied to RAM at boot time, when the message "Loading Operating System..." is displayed during ~8 seconds. The RAM is also used as temporary storage transparently for the user as described above. The file system compressed in the OS image may also be uncompressed to RAM at boot time when the message "Preparing file system, please wait..." is displayed during ~2 seconds to setup the OS file system. Since 2 seconds is quite fast, only part of the compressed files may be uncompressed (for example only the needed locale). For information the whole compressed file system (including the TI-84 Plus archive memory) is 2363.4KB once uncompressed.
We need your help
- Most of this page is speculation for the moment. Bring your own ideas.
- How many "storage capacity" and "space used" the TI-Nspire CAS advertises in the Handheld Status dialog? Does it confirm the thoughts based on the figures for the TI-Nspire?