Sharp MZ-2861
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| An MZ-2861 with its keyboard (photo: Nobuaki Ohishi) | |
| Specifications | |
|---|---|
| Manufacturer | Sharp |
| Type | 16-bit personal computer with an 8-bit MZ-2500 mode |
| Released | 1987[1] |
| Intro price | 328,000 yen[1] |
| CPU | Intel 80286 at 8 MHz; Z80B at 6 MHz in MZ-2500 mode[1] |
| Memory | 768 KB main RAM (2 MB with Sharp options); 512 KB graphics RAM; 14 KB text RAM and PCG[1] |
| Storage | Two built-in floppy drives[2] |
| Display | Text 80 or 40 columns by 25, 20 or 12 lines; graphics up to 640 × 400 in 16 colours, or in 65,536 colours[1] |
| Sound | YM2203 (3 FM and 3 SSG channels)[1] |
| ROM | 64 KB IPL and IOCS; 256 KB kanji ROM; 256 KB dictionary ROM[1] |
| FPU / coprocessor | 80287 (option, MZ-1M12)[1] |
| Power | AC 100 V, 50/60 Hz, 50 W[1] |
| Dimensions | 350 × 345 × 130 mm (main unit)[1] |
| Weight | 8.1 kg (main unit), 1.5 kg (keyboard)[1] |
| OS / Firmware | MS-DOS 3.1[1] |
| Predecessor | Sharp MZ-2500 |
| Model no. | MZ-2861 |
The Sharp MZ-2861 is a 16-bit personal computer that Sharp released in Japan in 1987 as the MZ-2800 series, nicknamed MZ Shoin after the Shoin word processor supplied with it.[1][2] It was designed around the Intel 80286, and a second processor, a Z80B, gives it an MZ-2500 mode in which it works as an 8-bit Sharp MZ-2500. A switch on the front panel selects the mode.[1] It was the last machine in the MZ series.[1] Sharp shipped it with MS-DOS 3.1, BASIC-M28, the Shoin 28 word processor and a program that emulated the NEC PC-9801 in software.[1]
Hardware
[edit | edit source]In 16-bit mode the MZ-2861 runs an 80286 at 8 MHz, with a socket for an 80287 maths coprocessor (Sharp's MZ-1M12). It has 768 KB of main memory as standard, 512 KB of graphics memory, a 64 KB IPL and IOCS ROM, 256 KB kanji and dictionary ROMs, a µPD71071 DMA controller and a YM2203 sound chip.[1] Nobuaki Ohishi's comparison of the MZ-2800 and MZ-2500 boards shows the MZ-2861 keeping the MZ-2500's floppy controller (MB8876), keyboard and serial chips (LH0081B, LH0084B), YM2203, 8-bit memory and I/O controllers and text and graphics controllers, and adding a system controller, a combined 8255, 8253 and 8259 (MN12861), an 8259 interrupt controller, the µPD71071, and further Sharp custom chips for I/O, disk and joystick, printer, graphics display and character control. Its key controllers are different parts (LZ91A56 in the main unit and LZ91A55 in the keyboard).[2]
The machine has two 8-bit expansion slots compatible with the MZ-2500's, provided by the optional MZ-1U09 frame, and three 16-bit slots that Japanese Wikipedia describes as PC-9801-compatible.[1] Ohishi's comparison of the 16-bit slot with the PC-9801's C-bus found the signals largely the same, with fewer interrupt lines and only DMA channel 3, and found that the I/O devices carried over from the MZ-2500 are decoded on the low 8 address bits only.[2]
Connections
[edit | edit source]| Connector | Type |
|---|---|
| Printer | Centronics-type, Sharp 25-pin D-sub |
| RS-232C | 25-pin D-sub |
| External floppy drive | Sharp 37-pin D-sub (no matching drive was sold) |
| Joystick | Two Atari-type 9-pin D-sub |
| Mouse | Sharp 8-pin mini-DIN |
| Keyboard | Sharp connector |
| Colour and monochrome CRT | 8-pin DIN each |
| CRT control | 8-pin DIN |
MZ-2500 mode
[edit | edit source]In MZ-2500 mode the MZ-2861 runs MZ-2500 software, but it does not support the MZ-2500's data recorder.[2][3] Boards that work in an MZ-2500 can fail in its 8-bit slots. On the MZ-2861 the read and write strobes on these slots are already combined with the I/O request line, so a Z80 PIO on a board sees the conditions for its built-in reset during the M1 wait cycles and keeps resetting.[1][2] The problem showed up with an intelligent MIDI board that the Hoshikuzubako circle developed on an MZ-2500; Ohishi describes curing it on the board by combining the read line with the memory request signal.[2] Sharp's MZ-1E30 hard disk interface works in both machines; its ROM jumper must be moved to the OFF position for the MZ-2800.[4]
Boot devices
[edit | edit source]Oh!MZ for June 1987, as summarised by Ohishi, lists the devices the MZ-2861 can start from, in order of priority, with the letter that selects each one when held at reset:[2]
| Priority | Device | Key |
|---|---|---|
| 1 | Internal floppy drive #0 | A |
| 2 | Internal floppy drive #1 | B |
| 3 | Hard disk #0 (external, option) | C |
| 4 | Hard disk #1 (external, option) | D |
| 5 | External floppy drive #2 (option) | K |
| 6 | ROM disk (internal, option) | R |
Only the first three appear in the MS-DOS manual supplied with the machine.[2] When a machine will not boot from its hard disk, holding C at reset skips the floppy drives and tries hard disk #0 directly.[2]
Service notes
[edit | edit source]- The MZ-2861 is rated for 100 V mains at 50 or 60 Hz and 50 W.[1] Outside Japan it needs a step-down transformer.
- The 8-bit side uses the same floppy controller, keyboard, serial and sound chips as the Sharp MZ-2500.[2] For the start-up keys and messages of MZ-2500 mode, see the Sharp MZ-2500 Troubleshooting Guide.
Documentation
[edit | edit source]- The owner's manual (B5, 169 pages).[5]
- I/O magazine, June 1987, printed a review of the MZ-2861 with circuit diagrams, and Oh!MZ for the same month carried technical information.[2] The I/O issue is on the Internet Archive.[6]
Related pages
[edit | edit source]- Sharp MZ-2500, the predecessor, whose software runs in MZ-2500 mode
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 MZ-2861, Wikipedia (Japanese)—link(accessed 2026-10-21) Released 1987; 16-bit machine with an MZ-2500 mode in which it works as an 8-bit machine; nicknamed MZ Shoin for the bundled Shoin word processor; last of the MZ series; designed around the 80286; mode selected with a switch on the front panel; styling and keyboard layout follow the MZ-2520; specifications (80286-8 in a 68-pin PLCC with optional 80287, Z-80B at 6 MHz in MZ-2500 mode; 768 KB main RAM, up to 2 MB with Sharp options; 512 KB graphics RAM; 14 KB text RAM and PCG; 64 KB IPL/IOCS ROM; 256 KB kanji ROM; 256 KB dictionary ROM; µPD71071 DMA controller; YM2203; AC 100 V 50/60 Hz, 50 W; 10 to 35 °C; main unit 350 × 345 × 130 mm, 8.1 kg; keyboard 410 × 196 × 38 mm, 1.5 kg; 328,000 yen); interfaces; bundled software (MS-DOS 3.1, BASIC-M28, Shoin 28, PC-9801 emulator); options; the Z80 PIO incompatibility of the 8-bit slots in MZ-2500 mode; the 8-bit slots are an option (MZ-1U09).
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 MZ-2800– Nobuaki Ohishi, Nibbles lab. Sharp museum—link(accessed 2026-10-21) The MZ-2800 (model MZ-2861) appeared in spring 1987; it has an MZ-2500 mode selected with a front switch, usable as an MZ-2500 apart from the data recorder and some other parts; the 8-bit slots take MZ-2500 boards, but the read and write strobes on them are combined with IORQ, so a Z80 PIO on a board is reset during M1 wait cycles; cure by ANDing the IOR line with MREQ; the 16-bit slots are close to the PC-9801's C-bus, with fewer interrupt and DMA lines; I/O addresses decoded on the low 8 bits; list of LSIs used in the MZ-2800 and the MZ-2500; boot devices from Oh!MZ June 1987 (internal drives #0 and #1 as A and B, hard disks #0 and #1 as C and D, external drive #2 as K, ROM disk as R, in that order of priority, with the letter held at reset to choose a device); I/O June 1987 printed a review with circuit diagrams; Nikkei Personal Computing reported shipment from mid-May 1987 and a PC-9801 emulation program running a handful of programs at launch.
- ↑ MZ (コンピュータ), Wikipedia (Japanese)—link(accessed 2026-10-21) Model list: MZ-2861 (MZ Shoin), 1987, separate main unit and keyboard, MZ-2500 compatible mode with both a Z80 and an 80286, MS-DOS and PC-9801 emulation in 16-bit mode, the MZ-2500's data recorder not supported, the only 80286 machine in this line of the MZ series.
- ↑ MZ-1E30– Nobuaki Ohishi, Nibbles lab. Sharp museum—link(accessed 2026-10-21) SASI hard disk interface for the MZ-2500 and MZ-2800; the ROM on the board is the MZ-2500 IPL extension, and the jumper beside it is moved to OFF for use in an MZ-2800; 50-pin card edge; the SASI connector needs the special slot cover supplied.
- ↑ MZ manual PDF project– Nobuaki Ohishi, Nibbles lab.—link(accessed 2026-10-21) MZ-2800 owner's manual, B5, 169 pages.
- ↑ I/O アイ・オー 1987年06月号, Internet Archive—link(accessed 2026-10-21) Scan of I/O for June 1987, which contains the "New Machine MZ-2861" article.