Disclosed is an inkjet print cartridge having an ink reservoir; a substrate having a plurality of individual ink firing chambers with an ink firing element in each chamber along a top surface of the substrate and having a first outer edge along a periphery of substrate; the first outer edge being in close proximity to the ink firing chambers. The ink firing chambers are arranged in a first chamber array and a second chamber array and with the firing chambers spaced so as to provide 600 dots per inch printing. An ink channel connects the reservoir with the ink firing chambers, the channel including a primary channel connected at a first end with the reservoir and at a second end to a secondary channel; the primary channel allowing ink to flow from the ink reservoir, around the first outer edge of the substrate to the secondary channel along the top surface of the substrate so as to be proximate to the ink firing chambers. A separate inlet passage for each firing chamber connecting the secondary channel with the firing chamber for allowing high frequency refill of the firing chamber. A group of the firing chambers in adjacent relationship forming a primitive in which only one firing chamber in the primitive is activated at a time. A first circuit on the substrate connects to the firing elements and a second circuit on the cartridge connects to the first circuit for transmitting firing signals to the ink firing elements at a frequency greater than 9 kHz. When operating the print cartridge, the substrate is able to dissipate more heat, since the ink flowing across the back of the substrate and around the edges of the substrate acts to draw heat away from the back of the substrate.