The Sharp MZ-2500, launched in Japan in 1985 but never available to the general public in the U.K., was also referred to as their ‘SUPER-MZ‘ machine. It was the last in a very long line of Sharp Z80-based computers, and was one of the most sophisticated Z80 Computers ever produced anywhere in the world.

For many years the MZ-2500 remained a mystery to virtually everyone outside Japan. As far as the SUC were concerned the veil began to lift in December 1994 when we were invited to the Sharp factory in Wrexham to pick up a ‘pallett-load‘ of Sharp computers that were about to be scrapped. When we arrived on site we found that the offering included two MZ-2500 base units and an MZ-2500 keyboard with no lead.

Back at John‘s home in Codsall, we assembled a temporary 100V 50Hz supply and used it to fire up one of the MZ-2500 Base Units. This seemed to be in working order and eventually, by trial and error, we found that an MZ-5600 Mono Monitor worked on the MZ-2500 and revealed the IPL start-up message ‘Insert System Disk‘ - but we had no disk and no keyboard, so all we could do was sit and stare at the message!

And thus things remained for 3 years. Then, in December 1997, I received an SOS from Manchester, from someone who was still using an MZ-2500 to control a ‘Pick and Place‘ machine in his PCB factory, and needed help to rewrite the machine-code bits of its mainly ‘BASIC‘ program to suit a modern IBM-compatible computer.

I managed to sort out the problems and early in 1988, as a reward, I received a large parcel from Manchester containing three MZ-2500 base units, an MZ-2500 keyboard with a lead attached, a small MZ-2500 Monitor and, most importantly of all, an MZ-2500 BASIC Operating System disk and a few pages of documentation.

Armed with all these goodies it did not take me long to cobble together a special MZ-2500 version of Tanswell‘s Disassembler complete with a bank-switching option that enabled me to unravel the memory map of the MZ-2500. My findings were quickly confirmed by a chance E-mail from Japan which stated, inter alia, that the MZ-2500 has 128KB RAM ( expandable to 256K ) and 64K of VRAM ( expandable to 128K ).

We still do not have an official Sharp Brochure on the MZ-2500, nor do we have a Manual. But from its BASIC operating system disk, the skeleton documentation from Manchester, the Japanese E-Mail, and experiments with the special MZ-2500 version of Tanswell‘s Disassembler, we now know that:-

The SHARP MZ-2500 is based on one or more Z80 processors running at 6MHz.

It has a BASIC operating system labeled‘6Z002 V1.0C‘. ( the part number ‘6Z002‘ probably implies that Sharp adopted ‘6Z‘ as the identifier for all their 3.5" software, but we do not yet have enough evidence to be certain on this point ).

We believe that there was also a PCP/M system for the MZ-2500 ( we have a Manual for this system - in Japanese - but no System disk and no other information ).

The 6Z002 Basic Operating System is capable of bank-switching Z80 memory in blocks of 8K. In theory it can handle 64 blocks to give a total capacity of 512K RAM / ROM; but on our machine it seems to utilize only 52 blocks, giving a total capacity of 416K. These 52 blocks are utilized as follows:-

Blocks $00 - $0F, 16 blocks 128K RAM built-in
Blocks $10 - $1F 16 blocks 128K RAM on optional extra card MZ-1R26
Blocks.$20 - $2F 16 blocks 128K VRAM half on-board half on optional extra card MZ-1R27
Blocks $34 - 37 4 blocks 32K ROM built-in IPL / Monitor / FP-Package

The first 48 blocks listed above match the skeleton information that came to us by E-mail from Japan, and include the standard 128K RAM ( expandable to 256K ) and the standard 64K VRAM ( expandable to 128K ). The other 4 blocks cover the built-in 32K ROM, which, as far as built-in ROM is concerned, is about ‘par‘ for Z80 machines designed around 1984 - 5. The total memory is thus 384K RAM plus 32K ROM = 416K.

However, this may not be the complete picture as some rudimentary bank-switching experiments performed via the special Disassembler suggest that our MZ-2500, as it is currently set up, may also be able to use blocks $30 - $33 and $38 - $3A. If this turns out to be the case the total memory capacity of the machine becomes 472K.

And there is still one vacant slot on our MZ-2500 motherboard, marked ‘MZ-1M10‘. At this moment we have only one rather vague pointer to what this slot may be for - a brochure for Sharp‘s slightly earlier but highly compatible MZ-2200 computer, which shows an optional extra ‘16-Bit Kit‘ board with the part number ‘MZ-1M01‘.

It therefore seems possible that the ‘MZ-1M10‘ slot on our MZ-2500 may be intended for an optional extra ‘16-Bit Kit‘ board that might utilize memory blocks $3B - $3F. If that were so it would explain why the BASIC software is theoretically capable of switching up to 64 blocks and 512K of memory.

Earlier this year, a very good friend who specializes in close-up photography of antiques took some shots of my MZ-2500 as it sat on my patio table, basking in the spring sunshine. These photographs are reproduced on the opposite page:-

TOP PHOTOGRAPH
( general view of a complete unit from Manchester ):-

The base unit is ‘MZ-2500 V2‘; the small mono Monitor is ‘MD-9P1‘; the characters on the label beneath the Keyboard are all Japanese, except for the name ‘MZ-2500‘.

MIDDLE PHOTOGRAPH
( close-up view of the Main unit from the front )

LEFT POWER ON / OFF button, EARPHONE and MICROPHONE facilities
CENTER TAPE counter and controls, MODE / RESOLUTION / VOLUME / RESET panel
RIGHT TWO 3.5“ built-in DISK drives, KBD socket, MOUSE socket

The facilities on the MODE / RESOLUTION / VOLUME / RESET panel are ( from L to R ):

MODE ( 3-way Switch ) MZ-2500 / MZ-2200 / MZ-80B
RESOLUTION ( 2-way Switch ) Standard / High
VOLUME ( Slider ) 0% - 100%
RESET ( Push-button ) RESET to System
IPL ( Push-button ) RESET to IPL

The MODE switch is very useful as it allows the MZ-2500 to emulate either the MZ-2200 or the MZ-80B, and thus facilitates software transfer between these machines.

BOTTOM PHOTOGRAPH
( close-up view of the Main unit from the rear ):-

The labels are clearly visible and most of them need no explanation. However, it is worth noting that, in addition to the usual Printer RS-232 and Monitor sockets, there are also sockets for external FDD‘s, Joysticks, ‘TV Control‘ ‘Voice‘ and ‘Audio‘, as well as, top left, an expansion unit for further add-ons ( which currently holds a general-purpose I/O card of unknown design ).

Sharp Users Club General Section MZ-Computer time Chart

The chart below, showing the development of Sharp MZ-computers during the period 1978 - 1985, has previously appeared in two earlier issues ( Vol. 18 / 1 and 19 / 3 ).

However, with the publication in this issue of new information on the MZ-40K and MZ-2500, the first and the last of the Sharp MZ-computers, it seems appropriate to reprint this chart yet again, together with the table of technical details that accompanied the chart on the occasion of its first appearance in Vol.18 No.1.

We hope this reminder will be especially helpful to the new members who have joined the SUC during the last 3 years.

(*) On the X1 TURBO models the 32K ROM includes die IPL ( and other programs ? ).
(**) On the MZ-2500 the 32K ROM includes die IPL, Monitor & FP Package
(***) On the PC-3200 the 32K ROM includes BASIC.

The MZ-2000 is very similar to the MZ-80B, but with the tape vertically oriented and a different keyboard. An MZ-2000 master disk is 280K, the same as the MZ-80B.