an inquiry / is there a mistake?

Hello native speakers,

Please explain me the sentence's part I underlined below. It must be surely a mistake, mustn't it?
Or maybe the author wanted to write >to be doing some work< ?

thank you in advance,
Jacek

>> The chip maker estimates that a single instruction thread only uses around 35 per cent of a processor's available resources. Running a second thread allows those otherwise idle circuits to be do some work.<<