Complex sentence: With buffering, the card reader control could be overlapped with processing, and the reader could be run at full speed through large data decks, but memory for the more complex program and for buffers was often at a premium.
Split into simpler sentences: With buffering, the card reader control could be overlapped with processing, and the reader could be run at full speed through large data decks. But memory for the more complex program and for buffers was often at a premium.