The PDA of tungsten

As this analysis is going to be deep, advance payment that is going away to treat the resumptions that randomly undergo the users of Palms with the new system of memory NVFS (especially both first equipment implemented that it: the Tungsten T5 and Treo 650), the cause of the same, and how they are possible to be solved.

From the launching of the Tungsten T5, there by the 2004, Palm the novel system of denominated memory NVFS has implemented in its devices, that are the abbreviations of Non-Volatile File System. (The same type of memory that cards SD) like main memory of the PDA consists of the use of flash memory. The flash memory does not need continuous power supply to preserve the information, something that yes needed the previous used memory, of the type ram, similar to the one of the computers.

This has two advantages: smaller power consumption (and so the autonomy improves enormously), and that the content of the memory is not lost when the battery is run out completely. But the NVFS also brought disadvantages. More indeed, the implementation of the same. And to understand the problem, first we must know how it is exactly the new system of memory.

In PDAExpertos it is very well explained. I am going to summarize it to the minimum necessary to understand the rest of the analysis. For a reading in more depth, I recommend its article.

The Palm previous to the Tungsten T5 had the following scheme of memory:

• On the one hand a memory chip ROM with the operating system, programs and bookstores that came from factory. The rom memory, as its name indicates, is of read only, we cannot modify it.
• And a memory chip ram as well with two parts: the one that we really accede, where the programs settle, keep the documents, etc, and a small part to which we cannot accede, denominated Dynamic Heap, that is the used one by the programs when they are executed. Both parts could identify with the hard disk and the main memory of a computer, respectively.

The Palm with NVFS has another structure:

• A memory chip flash, in which it is, in a zone, the operating system, bookstores and programs that come from factory (comes to be the ROM of the previous models), and in another zone of the same, the memory for our use, where they keep the programs which we installed, the documents, etc. We say that it is as a hard disk of computer, in which the operating system is in a directory, and the other our programs and data.
• But it also continues being a memory chip ram. And you will ask yourselves why? The reason is that a program cannot directly be executed in the flash memory, must do it in ram. Therefore, whenever an application is executed, this one must copy first a ram. This makes our Palm of transparent way, and the delay that produces is imperceptible.
  This ram memory contains the Dynamic Heap that we commented before, and in addition a called zone DbCache that is where they are copied, like tenth, the programs to execute itself. Once we closed a program, flock of the DbCache to be done site to him to the following program that we execute (thus would have at least to be…). And this one cache is indeed the cause of all the problems.

In summary, the famous DbCache, of 10Mb, to which we cannot accede directly is, since we have seen, of internal use of the operating system. And the problems of “Not enought memory…” that it gives to the Blazer, or the resumptions by errors “Fatal Exception” or “Memory full” that takes place when we abrimos a program that consumes much memory, or without apparent cause in some cases, they must to his peculiar form of operation. But we will see that it in following post, because this one already has been made quite dense.

By: Tricks
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Labelling: memory, nvfs, palm, handspans, pda, problem

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