. x ▁for ▁Series ▁ 2 0 0 / 3 0 0 . ▁ 3 . x ▁( 1 9 8 8 ) ▁H P ▁ 9 0 0 0 ▁Series ▁ 6 0 0 / 8 0 0 ▁only . ▁Note : ▁ 2 . x / 3 . x ▁( for ▁Series ▁ 6 0 0 / 8 0 0 ) ▁were ▁developed ▁in ▁parallel ▁with ▁ 5 . x / 6 . x ▁( for ▁Series ▁ 2 0 0 / 3 0 0 / 4 0 0 ), ▁so , ▁for ▁example , ▁ 3 . x ▁was ▁really ▁contemporary ▁with ▁ 6 . x . ▁The ▁two ▁lines ▁were ▁un ited ▁at ▁H P - U X ▁ 7 . x . ▁ 6 . x ▁( 1 9 8 8 ) ▁Support ▁for ▁H P ▁ 9 0 0 0 ▁Series ▁ 3 0 0 ▁only . ▁Int rodu ced ▁so ckets ▁from ▁ 4 . 3 B SD . ▁ ▁This ▁version ▁( t ogether ▁with ▁ 3 . x ) ▁also ▁introduced ▁the ▁above - dis cuss ed ▁context ▁dependent ▁files ▁( C DF ), ▁which ▁were ▁removed ▁in ▁release ▁ 1 0 ▁because ▁of ▁their ▁security ▁ris ks . ▁ 7 . x ▁( 1 9 9 0 ) ▁Support ▁for ▁H P ▁ 9 0 0 0 ▁Series ▁ 3 0 0 / 4 0 0 , ▁ 6 0 0 / 7 0 0 ▁( in ▁ 7 . 0 3 )