Lol , for big maps we mean very large .img tiles,
for example. in this map
[Only registered and activated users can see links. ]
where all the unlockers in 32 bit OSes hanged on a very large .img tile: 08225032.img (1,028,160 KB).
That sub-part 69 in the unlocking process gave DIV BY ZERO exception error in Garmin Unlocker.
But since FIU vers v.1.3 ( I donnow Unl.Alt. corresponding version) with the help of 3GB switch in 32 bit OS , we can cope with these big parts. Np with 64 bit OSes.

Edit:Btw if you read WknThDg's post n 9 in this thread (he's using XP, if he didnt change recently)he unlocked the.img with FIU.