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4850 problem "checksumdifferencetoolarge"?

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#1
Trying to change clock & slightly up the volts on my non-ref sapphire 4850 512MB and its coming up with this;



Any ideas/tips? :toast:
 
Last edited:

BAGZZlash

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#2
Could you post the BIOS that produces this issue as well as what you tried to change in the BIOS as precise as possible?
 
Joined
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Location
Manchester, UK
Processor i7 920 D0 @ 3.2Ghz 0.95V / 4.45Ghz @ 1.35V
Motherboard Gigabyte EX58-UD3R
Cooling Xig s1283 with Push/Pull Fans
Memory 6GB Corsair XMS3 1600mhz
Video Card(s) HIS 6950 2GB @ 950/1300
Storage Samsung F3 500
Display(s) 24" Acer V243HLmb LED
Case CM690 modded for airflow
Audio Device(s) Xonar D1 -> Marantz CR502 -> B&W 686 + RSW12
Power Supply PC Power & Cooling Silencer 750
Software Win7 x64 Home Premium
Benchmark Scores SP1M - 10s AQM - 202,200 marks w/ 8800gs + E7300 3D '06 - 26,000 4890+4870
#3
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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BAGZZlash

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#4
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! :)
 

BAGZZlash

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#6
Out of curiosity, why does this happen? You're not able to modify a bios that has already been modified by RBE?
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.
 
Joined
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Location
Manchester, UK
Processor i7 920 D0 @ 3.2Ghz 0.95V / 4.45Ghz @ 1.35V
Motherboard Gigabyte EX58-UD3R
Cooling Xig s1283 with Push/Pull Fans
Memory 6GB Corsair XMS3 1600mhz
Video Card(s) HIS 6950 2GB @ 950/1300
Storage Samsung F3 500
Display(s) 24" Acer V243HLmb LED
Case CM690 modded for airflow
Audio Device(s) Xonar D1 -> Marantz CR502 -> B&W 686 + RSW12
Power Supply PC Power & Cooling Silencer 750
Software Win7 x64 Home Premium
Benchmark Scores SP1M - 10s AQM - 202,200 marks w/ 8800gs + E7300 3D '06 - 26,000 4890+4870
#7
Bought card 2nd hand, so assumed bios was unaltered :eek:

Can I load any sapphire bios onto this card?
 
Joined
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Location
Manchester, UK
Processor i7 920 D0 @ 3.2Ghz 0.95V / 4.45Ghz @ 1.35V
Motherboard Gigabyte EX58-UD3R
Cooling Xig s1283 with Push/Pull Fans
Memory 6GB Corsair XMS3 1600mhz
Video Card(s) HIS 6950 2GB @ 950/1300
Storage Samsung F3 500
Display(s) 24" Acer V243HLmb LED
Case CM690 modded for airflow
Audio Device(s) Xonar D1 -> Marantz CR502 -> B&W 686 + RSW12
Power Supply PC Power & Cooling Silencer 750
Software Win7 x64 Home Premium
Benchmark Scores SP1M - 10s AQM - 202,200 marks w/ 8800gs + E7300 3D '06 - 26,000 4890+4870
#9
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
 

blkhogan

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#10
BAGZZlash is the freaking man when it comes to this stuff. We are lucky to have him here. :respect:
 

BAGZZlash

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#11
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
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:
 
Joined
Apr 29, 2008
Messages
346 (0.10/day)
Likes
61
Location
Manchester, UK
Processor i7 920 D0 @ 3.2Ghz 0.95V / 4.45Ghz @ 1.35V
Motherboard Gigabyte EX58-UD3R
Cooling Xig s1283 with Push/Pull Fans
Memory 6GB Corsair XMS3 1600mhz
Video Card(s) HIS 6950 2GB @ 950/1300
Storage Samsung F3 500
Display(s) 24" Acer V243HLmb LED
Case CM690 modded for airflow
Audio Device(s) Xonar D1 -> Marantz CR502 -> B&W 686 + RSW12
Power Supply PC Power & Cooling Silencer 750
Software Win7 x64 Home Premium
Benchmark Scores SP1M - 10s AQM - 202,200 marks w/ 8800gs + E7300 3D '06 - 26,000 4890+4870
#12
Wow thanks you've been a fantastic help! :toast: