Area 64 Editorials

                                  As seen in  the Atari Jaguar FAQ by Robert Jung

Is the Jaguar really a 64-bit system?

The question is hard to resolve, largely because the definition of what constitutes an "N-bit" system has not been set. Of the five processors in the Jaguar, only the object processor and the blitter are "true" 64-bit components. Because the blitter and the object processor are in the Tom chip, by extension Tom is a 64-bit chip. Furthermore, the Jaguar also used a 64-bit memory architecture, according to Jez San of Argonaut Software.

Some say the Jaguar should be considered a 32-bit system, as that is the maximum register size in the programmable processors (the 68000, the graphics processor, and the DMA sound processor). Others say the Jaguar can be considered a 64-bit system, because 64-bit components are used, and the GPU can access 64 bits of data if required. Again, the lack of an agreed-upon definition serves to complicate the issue.

According to Jaguar designer John Mathieson, "Jaguar has a 64-bit memory interface to get a high bandwidth out of cheap DRAM. ... Where the system needs to be 64 bit then it is 64 bit, so the Object Processor, which takes data from DRAM and builds the display is 64 bit; and the blitter, which does all the 3D rendering, screen clearing, and pixel shuffling, is 64 bit. Where the system does not need to be 64 bit, it isn't. There is no point in a 64 bit address space in a games console! 3D calculations and audio processing do not generally use 64-bit numbers, so there would be no advantage to 64 bit processors for this.

"Jaguar has the data shifting power of a 64 bit system, which is what matters for games, so can reasonably be considered a 64 bit system. But that doesn't mean it has to be 64 bits throughout."

For the record, the opinion of most third party developers and observers is that the Jaguar is indeed a 64-bit system. The emphasis is on the word "system"; while not every component is 64 bits, the Jaguar architecture, as a COMPLETE SYSTEM, is.