MZ-3500

A Brief History of the MZ-3500

In the U.K., the MZ-3500 ‘rose without trace‘. lt was not reviewed in PCW nor,  as far as I know, in Practical Computing, and it was rarely advertised in any of the popular computer magazines. However, there was an advert in the July 1983 issue of PCW, by a firm called ‘Bits & P.C.s‘, which implied that at that time the MZ-3500 was STOP PRESS news, and quoted the following prices:

MZ-3500 with 128K RAM, Mono display,
FDOS, BASIC, CP/M & PEACHCALC £1795
Ditto, with colour display £2190
600 x 400 High Resolution Option £199
These prices are EX VAT; in the same Magazine the EPSON QX-10 with 256K RAM and no software is £1735

By July 1983 the 16-bit bandwagon was rolling, and a Z80 machine had to be something special to get noticed at all. The Epson QX-10 was in this category; its 256K RAM could be expanded to 512K, and it had excellent graphics and a bank-switching system that allowed it to run CP/M 3 ( CP/M PLUS ) with a TPA of 60K, and a RAM-disk.

No doubt, if the MZ-3500 had been reviewed, the fact that it had two Z80 processors and 128K RAM expandable to 256K would have impressed; but its FDOS and BASIC software, virtually the same as on the PC-3201, might not have impressed at first sight, though in fact it does include a remarkable arithmetical package which is accurate to a maximum of 12 s.f. and is also flexible enough to display answers to any desired precision below that figure, and round them up or down to your liking ( full details of this facility are given on pp. 16 – 19 of the MZ-3500 Owner‘s Manual ).

The CP/M 2.2 system supplied by Sharp might have caused some adverse comments, as it uses several non-standard screen control codes. Once again Microtechnology Ltd. came to the rescue; they wrote an alternative version of CP/M 2.2. which uses standard CP/M screen control codes and also includes utilities to allow the user to re-define one or both disk drives for other disk formats. Using these, the MZ-3500 can read CP/M data disks from the Sharp PC-3201 and the Sharp MZ-80B, and some other non-Sharp formats.

I bought my MZ-3500 in April 1991, for £70. lt has proved a reliable machine and has enabled me to do a lot of useful work for the S.U.C., but it has only a mono screen so I have not been able to explore the colour capabilities of the machine. I believe that, to do this, I would have to revert to the Sharp / Digital Research version of MZ-3500 CP/M 2.2, as this I think is the only version of MZ-3500 CP/M that can control a colour VDU.

The MZ-3500 has one minor deficiency – no RESET key. So if the machine happens to crash it has to be switched off and back on again. However, it does have a HALT key, which is only operative in FDOS and BASIC; I believe this can be rewired to act as a RESET key, but I have not actually done this modification on my machine.

As a collector‘s item, the MZ-3500 is a good example of the last generation of Z80-based business computers, with a colour / hi-res option, a separate keyboard including function keys and a number pad, built-in disk drives, built-in printer and RS-232 ports, and an FD expansion connector which allows the user to fit extra external disk drives. And its overall appearance is neat and tidy and would not look out of place on a businessman‘s desk today.