Abstract: A crossbar converter to format 32 bit raster formatted I/O data into 5.times.4 patch formatted eight bit pixel data enables a 160 bit wide pixel data bus to be used so as to attain a high bandwidth for I/O devices. By using the wide pixel data bus and patch format for I/O, the facilities of the an screen memory and an arbitrary shape clipper can be made available to process a real time video window on a high resolution, bit mapped display monitor. The crossbar converter can be used to convert the parallel input of standard I/O devices into patch format, (five by four by eight, for example). The thus converted I/O data may be used by an off screen memory and an arbitrary shape clipper at high transfer rates.