Data General Corporation
This is an original DG MicroNOVA and was manufactured in late 1979; the line originated in 1975. It is the direct predecessor to my MicroNOVA MP/100 . This example dates from late 1977.
As in the "standard" NOVA architecture, this is a 16- bit machine and has four 16- bit accumulators, a 15- bit Program Counter, and an I/O bus capable of addressing sixty- four devices. Implemented around the single- chip mN601 CPU, it executes the basic NOVA instruction set plus a set of stack instructions and single- precision unsigned multiply/ divide operations. The maximum amount of mainstore the MicroNOVA can address is 32kW (64Ko) as limited by the 15- bit mainstore address bus.
Unlike the classic bus structures of the "large format" NOVAs, the MicroNOVA's busses derive their basis from microprocessor design and use serial and multiplexed bidirectional architectures rather than dedicated unidirectional parallel lines. The I/O bus on the MicroNOVA is a 16-wire flat cable with DIP headers at both ends; the memory bus is 16 parallel bits wide and multiplexes the address and data onto the same lines.
This system came with the architectural maximum of 32kW of memory spread across four 8kW boards using 20-pin DIPs (the chips bear a proprietary DG number and I don't have a translation table handy). The refresh is handled by the CPU module. This is a complete system and has four 8-inch floppy drives (hard- sectored) and two serial interfaces.
These machines had available, as an option, a small hand- held "front panel" which mimicked the operations possible on a "classic" "lights- and- switches" console. This device functions as an I/O device and can be programmed by the operator to perform any manner of functions. The LED readouts monitor a single memory location and display its contents continually. This example lacks the programmable hand- held console.
Alternatively to the handheld console, a "soft control panel" could be installed into the machine. This is a small program which occupies 256 words of mainstore at the very top of the address space and masks any RAM which might interfere with its operation. The "soft control panel" utilises the main Teletype at I/O address 10 and 11 for interaction with the user. This system has the SCP installed in it. To boot the OS from the first floppy drive one merely types "33L" (Load from I/O device 33).
The raw execution speed of the MicroNOVA is about one third that of my Nova 840 and about half that of the Nova 1200 class .
My most sincere thanks go to Mr. Ed Cook who took the time to look me up
after reading a newspaper article on my hobby.