It depends on the model. I have a 622, it needs the purple card because the chip was made before the latest revision of the encryption.satcrazy said:
When my 622 was new it did not need a card. Then one day that version of the encryption was hacked which necessitated the distribution of the "purple cards". I have since had 2 replacement 622' both were shipped with a purple card in the slot.
Someone with a 722 or 922 can tell you if those need a purple card as well.
