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  1.    #1  
    This should be an easy one for the braintrust

    I come across the terms "RAM" and "ROM" in the forum routinely to describe the working memory of the device and the non-volatile storage. The RAM is conceptually the same as RAM in a PC -- memory used by the device and CPU when it is "on" to run programs (and other stuff). The "ROM" is for data storage, conceptually the same as a disk drive on a PC.

    Here's where I get a bit confused... The storage "ROM" really should be referred to as NVRAM, shouldn't it? That's what it is -- writable non-volatile RAM -- not a ROM (which is read-only). This is confusing because there is a ROM in the device (I think) that contains the an image of the factory software, and when you do a hard reset, this is copied into the NVRAM.

    So, I think the correct memory model of the 750 looks like this:

    RAM -- working memory
    NVRAM -- storage
    ROM -- original factory software (OS, etc.)

    Is that right?

    Finally, when you update the software on the phone, what you're doing is overwriting the OS, etc. in NVRAM. This obseletes what is in the ROM, so if you need to hard reset, you have to also re-apply the OS s/w upgrade again. Practical implication, for example, is if hard reset after a phone has been upgraded from WM5 to WM6, you'll have a WM5 phone again, and will have to do the upgrade again.

    Do I have this right?
  2. #2  
    You are close, but no-one uses real ROM anymore. Most devices use non-volatile RAM these days. When you flash your device with a new ROM image you are overwriting the content of the NVRAM, and deleting anything else which may have been in there.

    Therefore, if you do hard reset your device, you will still only have WM6. WM5 is gone for good.

    The difference between the storage accessible to you and the storage dedicated to the OS is only a matter or partitioning, and you can find many cooked ROM's which would increase the size of the partition available to the user for example.

    So, in short, there is just ram and NVRAM. Thats all.

    PS: I dont know if the boot loader is actual ROM, but I believe even that is flashable, so probably not.

    Surur
  3.    #3  
    Thanks for the clear explanation, Surur! I've been out of the chip-hardware world for awhile, and was not aware that ROMs (PROM too? probably EPROMs as well...) were basically no longer in use in favor of NVRAM.

    While it makes sense technologically, in an application such as this it's a tiny bit scary... With such a design, one can obviously screw up their device beyond salvation without sending it back to the factory.

    Saves cost tho...
  4. #4  
    Quote Originally Posted by dwallersv View Post
    Thanks for the clear explanation, Surur! I've been out of the chip-hardware world for awhile, and was not aware that ROMs (PROM too? probably EPROMs as well...) were basically no longer in use in favor of NVRAM.

    While it makes sense technologically, in an application such as this it's a tiny bit scary... With such a design, one can obviously screw up their device beyond salvation without sending it back to the factory.

    Saves cost tho...
    Yep, with every ROM upgrade there is a real possibility of "bricking" your device.

    Surur

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