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4850 problem "checksumdifferencetoolarge"?

Discussion in 'RBE' started by crush3r, Feb 26, 2010.

  1. crush3r

    crush3r New Member

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    Trying to change clock & slightly up the volts on my non-ref sapphire 4850 512MB and its coming up with this;

    [​IMG]

    Any ideas/tips? :toast:
     
    Last edited: Feb 26, 2010
  2. BAGZZlash

    BAGZZlash RBE Author

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    Could you post the BIOS that produces this issue as well as what you tried to change in the BIOS as precise as possible?
     
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  3. crush3r

    crush3r New Member

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    Here's the original bios file and i was changing the values as shown in the ss in first post, 3d to 1.158V (does this actually increase volts at all?) and 700/1100 and lowering 2d to 250/500 at 0.968V :toast:
     

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  4. BAGZZlash

    BAGZZlash RBE Author

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    This BIOS is in no way a "stock" BIOS. It has been modified using RBE before, possibly even for many times. Load it into RBE, the "BIOS had been pre-modified using RBE" checkbox tells you I'm right.
    Checksum correction bytes are used up now. Just do what RBE's error message tells you to: Use the unmodified original BIOS of that card for RBE and be happy! :)
     
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  5. angelkiller

    angelkiller

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    Out of curiosity, why does this happen? You're not able to modify a bios that has already been modified by RBE?
     
  6. BAGZZlash

    BAGZZlash RBE Author

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    Yes, you can!
    But not for an infinite number of times. You see, every time you modify a BIOS using RBE and save it, RBE levels out the BIOS' checksum so that it always stays the same. That way RBE assures that the BIOS can be flashed to the card without the need of a "force flash".
    To level out the checksum, RBE determines if the checksum of the changes made is lower or higher than the original checksum. After that, it uses a set of bytes in the BIOS known to be useless (there are many useless bytes in the BIOS - oftentimes, certain sections of code need to be at a particular offset [position] in the BIOS, so there are bytes to fill up the file until this offset is reached) and writes values there to balance the checksum.
    However, this number of known useless bytes is limited. After changing and saving the same BIOS over and over, those free bytes are "depleted" at some point.

    So, even if modifying a pre-modified BIOS is possible maybe for ten, twenty or fifty times, it is always recommended to use a plain copy of the BIOS for any modification.
     
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  7. crush3r

    crush3r New Member

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    Bought card 2nd hand, so assumed bios was unaltered :eek:

    Can I load any sapphire bios onto this card?
     
  8. BAGZZlash

    BAGZZlash RBE Author

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    Oh, I see... :laugh:

    Yes, can do.
    Listen, I manually reset most of those bytes in your BIOS, so you should be good to go for several more times now. Cool? :cool:
     

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  9. crush3r

    crush3r New Member

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    Great! thanks bagzz, a few minutes ago i loaded te sapphire toxic bios onto the card, upping the volts too but i still have the 700Mhz cap on the core in CCC, will the bios you provided remove this cap? Thanks
     
  10. blkhogan

    blkhogan New Member

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    If I told u.. I'd have to kill u
    BAGZZlash is the freaking man when it comes to this stuff. We are lucky to have him here. :respect:
     
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  11. BAGZZlash

    BAGZZlash RBE Author

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    You'd like to overclock using the CCC (overdrive)?
    Your BIOS exhibits overdrive limits of 700/1.200 MHz for GPU/RAM. Using RBE, you can extend these limits. Load the BIOS, open the "Additional features" tab and use the Method 1 overdrive hack to do this. For the 4850, RBE has a cool built-in signature (800/1.300 MHz) so you don't even have to load a signature from the internet or from some other BIOS. Be sure to read the respective section about this in the tutorial to find out how it can be done in detail. :toast:
     
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  12. crush3r

    crush3r New Member

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    Wow thanks you've been a fantastic help! :toast:
     

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