System for improving the speed of data processing

An apparatus includes a first processing device to perform halftoning on a first set of values corresponding to a first set of pixels and a second processing device to perform halftoning on a second set of values corresponding to a second set of pixels, with ones of the first set of pixels located adjacent to the second set of pixels and with ones of the second set of pixels located adjacent to the first set of pixels. The apparatus further includes a bus arranged for transferring a third set of values, from the halftoning of ones of the first set of values corresponding to the ones of the first set of pixels, to the second processing device and for transferring a fourth set of values, from the halftoning of ones of second set of values corresponding to the ones of the second set of pixels, to the first processing device.