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  1.    #1  
    I've taken a break from the Linux porting stuff and written an article that describes exactly how DBCache, free NVFS space and dynamic RAM are affected by custom ROMs and how it relates to the underlying storage technology.

    If you like to hack your own ROMs, this is a good way to learn about what really happens under the hood.

    http://www.grack.com/blog/articles/2...e-and-rom-size

    If you have any comments or questions, feel free to post them here. If you'd like me to expand on anything, let me know.
    Last edited by mmastrac; 02/07/2006 at 04:05 PM.
  2. #2  
    Quote Originally Posted by mmastrac
    Once you have stripped your ROM, ensure that you are using a ROM updater that gives you the smallest possible ROM partition that still fits the size of your ROM.
    Where or how to find or get the proper "ROM updater" for a specific ROM size ?
  3.    #3  
    I'm still gathering some info with Shadowmite on that one, but for GSM ROMs, the latest Cingular update gives you approximately 1MB more than the latest ROW rom update.

    You can gain 1MB of NVFS right now by reflashing a ROW image with the cingular RomUpdaterApp (this assumes you've shrunk your ROM to fit in the smaller space by removing extra languages).

    I'll see what I can do for gathering RomUpdaterApps vs. max ROM size.
  4. #4  
    Thank you for this write-up. This explains a lot. Very well written.
  5. #5  
    Quote Originally Posted by mmastrac
    I'm still gathering some info with Shadowmite on that one, but for GSM ROMs, the latest Cingular update gives you approximately 1MB more than the latest ROW rom update.

    You can gain 1MB of NVFS right now by reflashing a ROW image with the cingular RomUpdaterApp (this assumes you've shrunk your ROM to fit in the smaller space by removing extra languages).

    I'll see what I can do for gathering RomUpdaterApps vs. max ROM size.
    That'd be great if you could find out which ROM updaters corresponded to what ROM/DBcache size.
  6. #6  
    Yes, that would be super. I have a custom ROM I built that I suspect is just a tiny bit too big and have been waiting until I have lots of spare time to try it because I expect I will have to use Shadowmite's restore tool to recover if it is too big. This might save me some bother.
  7. #7  
    So to put it in dummy's terms...

    You have RAM - Free space to add programs
    You have ROM - Storage space
    You have a DBcache size- calculated leftover space used to run programs...

    If you make a custom ROM (without changing the partition of ROM/RAM by using a smaller ROM installer) and remove non-used files out of ROM, you do not give yourself any additional "free space/RAM", but you do increase your DBcache size which gives you more room to run programs.
  8.    #8  
    Quote Originally Posted by RicoM
    So to put it in dummy's terms...

    You have RAM - Free space to add programs
    You have ROM - Storage space
    You have a DBcache size- calculated leftover space used to run programs...

    If you make a custom ROM (without changing the partition of ROM/RAM by using a smaller ROM installer) and remove non-used files out of ROM, you do not give yourself any additional "free space/RAM", but you do increase your DBcache size which gives you more room to run programs.
    Absolutely! You nailed it. If you want more "free space", you'll need to use a different RomUpdaterApp (which I need to catalog).
  9. #9  
    Quote Originally Posted by RicoM
    So to put it in dummy's terms...

    You have RAM - Free space to add programs
    You have ROM - Storage space
    You have a DBcache size- calculated leftover space used to run programs...

    If you make a custom ROM (without changing the partition of ROM/RAM by using a smaller ROM installer) and remove non-used files out of ROM, you do not give yourself any additional "free space/RAM", but you do increase your DBcache size which gives you more room to run programs.
    Are you sure? Is it as simple as just making a smaller custom ROM or do you need to alter the ROMupdaterapp to let it know that you have a smaller ROM and to increase the size of the dbcache?

    Is dbcache calculated automatically based on the size of the actual ROM (custom) and not the expected size of the ROM (standard) as defined by the romupdaterapp?
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    #10  
    Wow. Very nice writeup.

    This together with the fat32 thing, might drive me to a custom rom.
    Less than 400 posts to get my own little treo icon!
  11. #11  
    Wow...very informative. I guess the absolute minimal Rom then is the way to go with dbcache valued much more than storage space...
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  12. #12  
    Quote Originally Posted by gfunkmagic
    Wow...very informative. I guess the absolute minimal Rom then is the way to go with dbcache valued much more than storage space...
    Agreed, this dispells many myths ive heard about DBCache and ROM creation. I'll be pulling every app i put in my ROM out and pushing them all to the SD card now that I will be able to access them even faster with the new driver.
    iPhone in the Washington DC area.
  13. #13  
    Thanks for the great info! I just tried this out and installed a quick minimal ROM on Sprint Treo 650 and gained about 2 MB of dbcache. Works great! Thanks again!
  14. #14  
    Out of curiosity, what did you put in your "minimal ROM"?

    With Sprint/Verizon it seems like there are fewer options for ROM customization (e.g. only 1 language) , so I never did more than a paper exercise to see what diff it would make. The FAT32 update has got me interested again.
  15. #15  
    Quote Originally Posted by tomvb2000
    Out of curiosity, what did you put in your "minimal ROM"?

    With Sprint/Verizon it seems like there are fewer options for ROM customization (e.g. only 1 language) , so I never did more than a paper exercise to see what diff it would make. The FAT32 update has got me interested again.
    I've done this as well and removed:
    AirSam files
    BGService files
    Clock files
    All language files but US
    GetBC files
    Handando files
    Multimail (VersaMail) files
    RealPlayer files
    SAMgr files
    Tutorial files

    Used to add a bunch of programs ot the ROM but with the lates revelations have eliminated them leaving only the bare ROM. Stability was never really an issue for me but now I expect it will be even better.
  16. #16  
    Thanks. What increase in dbCache did you get from this? Still use VersaMail and RealPlayer or dump them for Snapper and pTunes?
  17. #17  
    Quote Originally Posted by tomvb2000
    Thanks. What increase in dbCache did you get from this? Still use VersaMail and RealPlayer or dump them for Snapper and pTunes?
    dumped versamail and real for snapper and pTunes

    increase, if I remember correctly, was a little over 1 mg.
  18. #18  
    Quote Originally Posted by tomvb2000
    Out of curiosity, what did you put in your "minimal ROM"?

    With Sprint/Verizon it seems like there are fewer options for ROM customization (e.g. only 1 language) , so I never did more than a paper exercise to see what diff it would make. The FAT32 update has got me interested again.
    I pretty much did what treo2die4 did with his minimal ROM.
  19. #19  
    So the dbcache will automatically grop itself to the largest size possible given the size of the custom ROM? Only RAM size is affected by the parameters of the ROMupdaterapp?
  20. #20  
    Quote Originally Posted by 2000 Man
    So the dbcache will automatically grop itself to the largest size possible given the size of the custom ROM? Only RAM size is affected by the parameters of the ROMupdaterapp?
    That's what I understand and would also explain the large size of the dbcache on rumored Treo700p as well. I recall reading over at shadowmite irc that dbcache is no longer hard coded on only limited by overall size of DOC Nand as described by mmastrac...
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