if you want cfw update to official 3.55
go to here
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then chose the cfw you want i prefer kmeaw even though most will say rebug is better
rebug link
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kmeaw link
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if you want a different cfw
you can browse them here
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if you dont know how to update
put a folder called PS3 on your usb stick
iside the folder make another folder called UPDATE
put the PS3UPDAT.PUP in the update folder
please notE rebug will need to be renamed to PS3UPDAT.PUP
Start with 3.55 and then just delete the pup from update and then put the other in its place when done