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 Johns 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
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 Tanswells 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 Tanswells
Disassembler, we now know that:-
The SHARP MZ-2500 is based on one or more Z80 processors running
It has a BASIC operating system labeled6Z002 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
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 Sharps
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.