Sharp MZ

~ the last words ~

In may 1978 Sharp put a 4-bit trainer kit on sale called the MZ-40K, sold under the name Microcomputer Doctor, built around a Fujitsu MB8843 with a hexadecimal keypad for input. The MZ in the name is usually explained as Microcomputer Z80, which is wrong, because there was no Z80 in it. The code had been registered for a bath buzzer and was sitting unused, so it got handed to the computer people because it was there. That is where the whole line starts.

It starts sideways as well as cheaply. The MZ-40K came out of a components division whose job was selling parts, not finished machines, and to avoid a fight with the division that handled calculators the follow-up was presented as a training kit for engineers rather than as a product. That follow-up was the MZ-80K of 1978, a half-assembled kit at 198,000 yen with the display and the cassette deck sharing one case, and with a keyboard you were expected to put together yourself. It established the line, and it went to Britain, where for a while it split the market with the TRS-80.

The design decision it is remembered for was not a design decision. The MZ-80K prototype had BASIC burned into ROM like everything else of the period. Sharp bought its ROM chips from outside suppliers, and a bug discovered in a mask ROM after production would have written off the entire order, so the shipping machine got a minimal monitor in ROM and nothing else, with the language loaded from cassette every time you switched it on. Japanese marketing later named this the clean computer and sold it as flexibility. Both accounts are true. It was a hedge against a supplier invoice, and it also meant Hudson Soft and Carry Lab could sell you a language Sharp had not written, on a machine Sharp could not lock.

I have never touched one of these. The MZ-700 was on British shelves in 1983 when I was not yet in school, and by the time I had a computer of my own the entire question had been settled by machines that booted into an operating system nobody could replace. What stays interesting is where the good part came from. Nobody in that building set out to build an open machine. Somebody worked out what a mask ROM revision would cost and decided not to carry the risk, and the consequence was a computer whose software layer belonged to whoever wanted it. I write firmware for hardware that goes out of reach after it ships, and the same calculation is on the table every time. What you can patch later is not an engineering preference. It is a number somebody in procurement has already worked out, and the architecture arrives afterward to justify it.

~ the record ~

~ why nothing was in ROM ~

The cost of the clean computer was paid by the user. With no BASIC in the machine, switching it on got you a monitor with six commands, and getting to a usable prompt meant waiting several minutes while the built-in data recorder loaded a language off tape. A floppy drive brought that down to roughly ten seconds, which most owners could not afford. From the MZ-80B onward Sharp pushed it further and put only an initial program loader in ROM, so even the monitor was read into memory at startup.

The reversal is the funny part. By the time of the MZ-2500 the hardware had become complicated enough to need a resident BIOS to support it, so a ROM went back into the machine after all, and the last MZ computers work the way the first prototype was going to before the accountants got to it.

~ the Argo ~

Sharp gave the series its own mark when the MZ-80K launched, because the company name alone was reading as a domestic-appliance brand and would not carry a computer. The design chosen was the Argo, the ship from the Greek myth, standing in for the sort of venture Sharp wanted the line to look like. It stayed on every machine to the end. On the MZ-2500 and the MZ-2861 there is a key on the keyboard with the ship printed on it.

~ Europe ~

The MZ sold outside Japan in a way most Japanese eight-bit machines never did, particularly in West Germany and Britain. In 1983, in the middle of the British home-computer boom, the MZ-700 came tenth in the year's sales chart out of twenty machines counted, ahead of the Apple IIe and ahead of the TI-99/4A. That is a Japanese computer beating American computers in a British market that was actually being won by Sinclair, which is a strange enough position to occupy that almost nobody remembers it happened.

The MZ-700 is also the one with the plotter. An optional four-color pen unit fitted inside the case and drew with ballpoint refills, which put color plotting into a home at a price where color plotting had no business being.

~ the last real one ~

The line ends properly in 1987 with the MZ-2861, a hybrid carrying both a Z80 and an Intel 80286, able to run MS-DOS and to emulate a PC-9801 well enough to be useful. It is an eight-bit product with a sixteen-bit escape hatch bolted to it, which is what the end of an architecture looks like from inside.

The badge survived a little longer than the machine. In 1988 Sharp shipped an MZ-8000 series that was a PC/AT compatible built to the Japanese AX standard, sharing nothing with the MZ except three characters in the model number. By then Sharp's television division had shipped the X68000 and the company's attention had gone there. Two divisions had been selling incompatible computers against each other since 1982, and this is which one lost.

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