Editing Data General Nova (section)

===Memory and I/O===
The smallest unit of addressable and writable memory is the 16-bit word; byte addressing is not supported. The first models were available with 8 [[kilo-|K]] [[word (computer architecture)|words]] of [[magnetic-core memory]] as an option, one that practically everyone had to buy, bringing the system cost up to $7,995.

This core memory board was organized in planar fashion as four groups of four banks, each bank carrying two sets of core in a 64 by 64 matrix; thus there were 64 x 64 = 4096 bits per set, x 2 sets giving 8,192 bits, x 4 banks giving 32,768 bits, x 4 groups giving a total of 131,072 bits, and this divided by the machine word size of 16 bits gave 8,192 words of memory.

The core on this 8K word memory board occupied a centrally located "board-on-a-board", 5.25" wide by 6.125" high, and was covered by a protective plate. It was surrounded by the necessary support driver read-write-rewrite circuitry. All of the core and the corresponding support electronics fit onto a single standard 15 x {{convert|15|in|mm|adj=on}} board. Up to 32K of such core [[random-access memory|RAM]] could be supported in one external expansion box. [[Semiconductor]] [[read-only memory|ROM]] was already available at the time, and RAM-less systems (i.e. with ROM only) became popular in many industrial settings. The original Nova machines ran at approximately 200 [[kilohertz|kHz]], but its SuperNova was designed to run at up to 3&nbsp;MHz when used with special semiconductor main memory.

The standardized [[backplane]] and [[input/output|I/O]] signals created a simple, efficient I/O design that made interfacing programmed I/O and Data Channel devices to the Nova simple compared to competing machines. In addition to its dedicated I/O bus structure, the Nova backplane had [[wire wrap]] pins that could be used for non-standard connectors or other special purposes.