High-Performance Embedded Computing

5.7 Memory Systems 309

The i960 is a 32-bit microprocessor that performs a variety of functions,

including rasterizing the page description language version of the plot into pix-

els. The pen control ASIC feeds pixel values to the inkjet heads. The i960 and

the pen control ASIC communicate through the swath RAM, which is not on the

i960’s main bus. Because the swath RAM feeds the inkjet pens as they move

across the page, its access times must be very reliable. If the swath were stored

in a memory on the i960’s bus, it would be subject to a variety of influences

from both the CPU and the I/O devices. Using a separate memory causes the

memory’s access ...