The 320xx is a series of microprocessors from National Semiconductor ("NS", "Natsemi"). The 320xx processors have a coprocessor interface which allows coprocessors such as FPUs and MMUs to be attached in a chain. The 320xx series was the predecessor of the Swordfish CPU.

Beginnings: the 32016 and 32032

The first chip in the series was originally called 16032, later renamed 32016. It became available in the late 1970s, and may have been the first 32-bit chip to reach mass production and sale (at least according to National Semiconductor marketing hype). This chip had a 16-bit external databus, a 24-bit external address bus, and a full 32-bit instruction set. The instruction set was extremely complex but mostly regular, with a large set of addressing modes. It was somewhat similar in spirit to (but not compatible with) the popular DEC VAX minicomputer instruction set.

National Semiconductor also produced related CPU-near chips like Floating Point Units (FPUs), Memory Management Units (MMUs), and Direct Memory Access (DMA) controllers. With the full set plus memory chips and peripherals, it was feasible to build a 32-bit computer system capable of supporting modern multi-tasking operating systems, something that had previously been possible only on expensive minicomputers and mainframes.

The 32032 arrived soon afterwards. It was almost completely compatible, but featured a 32-bit data bus (and a 31-bit address bus – TBC) for somewhat faster performance. Both the 32016 and the 32032 were notoriously unrealiable. There was a somewhat better chance of getting them to work if a full batch of CPU, MMU, FPU, and DMA chips were purchased as a matched, tested set, from Natsemi. Nonetheless, reliability trouble made the early 320xx's fairly unpopular, and Natsemi were forced to sell them at much lower prices than the competing Motorola 68000 in order to sell any at all. This low price did at least make them somewhat popular with hobbyists wanting to build 32-bit computers on a very small budget.

The 32332, 32532, and Swordfish

During the 1980s, successor chips called the 32332 and 32532 arrived, maintaining a good degree of compatibility, with much improved reliability and performance. By then the damage to reputation had been done, however, and these chips were (probably unjustly) ignored by most of the market. The Swordfish was a further advance, aimed at embedded systems and arriving circa 1990. This processor had some success in the laser printer market, despite intense competition from AMD and Intel RISC chips.

Similarly named non-NS processors

There was a totally unrelated processor series called 320xx made by Western Digital, another by Texas Instruments, and possibly some others made by various semiconductor companies — this may have stemmed from a feeling among CPU architects and marketers that a product designation beginning with the number thirty-two was the obvious naming scheme for series of 32-bit microprocessors.