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Brother 310 "Multiplier" Desktop Calculator

Brother 310
Image Courtesy of Serge Devidts, Calcuseum

The Brother 310 is a peculiar calculator - it does not have divison capability. The story behind this, and a number of other calculators that lacked division capability, lies in the development of a three-chip MOS LSI "multiplier" calculator chipset developed by Mitsubishi. It's not known if this chipset was purposefully developed lacking division, or perhaps had a bug in the implementation that caused division results to be incorrect that was found after a large batch of the chips had alreay been produced. However, there are some clues that perhaps the chipset was purposefully produced to omit division. One clue is the lack of a decimal point key on the keyboard. The lack of a decimal point key would indicate that perhaps division was not built-in to the chipset, because division operations have significantly less usefulness unless the ability to process fractional numbers is present. It is also a possibility that if the chipset indeed had a bug, that the specifications for the chipset simply did not mention the availability of input for a decimal point key. Whether by design, or an accident, this chipset did sell to Japanese calculator makers Brother and Denon. Denon's machine was the Denon DEC-311. Brother also sold the 310 as an OEM product to Remington, who marketed the machine as the Remington E-3.

The three Mitsubishi chips, part numbers MA8111, MA8112, and MA8113, were packaged in ceramic flat-pack packaging, with a rectangular package having long gold leads extending out from both long edges of the package. In the Denon calculator, the "higher-end" of these "no divide" calculators, the chips were retained in complex sockets that supported and connected the packages by the leads. Less-expensive versions, like the Brother 310 and the Remington E-3 (which was identical to the Brother 310 other than the name badge and model/serial number tag) had the chips soldered directly to the circuit board. The Brother 310 and its OEM copies (e.g., the Remington E-3) use seven-segment vacuum-fluorescent display tubes as opposed to the Nixie tube display in the Denon DEC-311. It isn't known if the Mitsubishi chipset provides some form of display mode select, allowing it to drive Nixie tubes (1-of-10 outputs) or seven-segment display technology depending on input to the chipset, or if the rendition of the display is determined entirely by the display driver circuitry located outside the chipset.

With technology advancing so quickly in these times, the notion of selling a "three-function" electronic calculator that could not divide was not a great strategy. With prices for full four-function electronic calculators in free-fall, why would anyone buy a calculator that could not handle fractional numbers, and didn't have the ability to do division, when for literally just a few dollars more, they could buy a full four-function calculator? It seems like the idea behind these machines was more of a marketing gimmick rather than having any real merit. Whatever reason drove the marketing of these rather odd chips and calculators, it likely will remain shrouded in the mists of time.