[flashrom] flashrom + bus pirate + winbond w25q64bv laptop ISP

Hi All - 
Been trying to dump out the bios on my asus G750JW laptop using flashrom + bus pirate.  The bios chip is Winbond w25q64bv.
No success until reading the ISP page and tried disconnecting Vcc, using laptop power and holding power button down on laptop.
Unfortunately the bios dump is good in the beginning but ends up being corrupted in the end with dummy data FF FF FF .... Does anyone have any suggestions on getting a good bios dump?
Thank you!Marc