I tried just upgrading the bios on my GF8200A with one downloaded from http://www.ecs.com.tw/ECSWebSite/Product/Product_DOWNLOAD.aspx?DetailID=873&CategoryID=1&DetailName=Feature&MenuID=24&LanID=9

And got the following error:

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steve@ultra ~/Downloads/bios $ sudo flashrom -p internal -w 78NA113.ROM
flashrom v0.9.9-rc1-r1942 on Linux 4.10.0-38-generic (x86_64)
flashrom is free software, get the source code at https://flashrom.org

Calibrating delay loop... OK.
Found chipset "NVIDIA MCP78S".
Enabling flash write... OK.
Found Winbond flash chip "W25X80" (1024 kB, SPI) mapped at physical address 0x00000000fff00000.
Reading old flash chip contents... done.
Erasing and writing flash chip... Erase/write done.
Verifying flash... FAILED at 0x00003f00! Expected=0xa1, Found=0xff, failed byte count from 0x00000000-0x000fffff: 0x5ec
Your flash chip is in an unknown state.
Get help on IRC at chat.freenode.net (channel #flashrom) or
mail flashrom@flashrom.org with the subject "FAILED: <your board name>"!
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DO NOT REBOOT OR POWEROFF!
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I got a similar error trying to reload a backup I'd just made with flashrom -r.  I then found another thread that mentioned to retry both the update & restore with the -VVV and -o options, so I retried twice, then retried the backup, but both also failed.