Amstrad Mega PC
 | |
| Mega PC 386SX system unit with the cartridge door and control pad sockets | |
| Specifications | |
|---|---|
| Manufacturer | Amstrad plc, under licence from Sega |
| Type | Personal computer with a built-in Sega Mega Drive |
| Released | 1992 (UK, per Sega Retro); 1993 (per Wikipedia) |
| Intro price | £999.99 (UK launch) |
| CPU | Intel 80386SX at 25 MHz (PC); Motorola 68000 (Mega Drive) |
| Memory | 1 MB, up to 16 MB in 30-pin SIMMs (four sockets per Amstrad; the board has positions for eight) |
| Storage | 40 MB hard disc; 3.5-inch 1.44 MB floppy drive |
| Display | — |
| Sound | AdLib-compatible FM (Yamaha YM3812); Mega Drive stereo |
| Graphics | Western Digital WD90C11 SVGA, 256 KB (512 KB option); Mega Drive video |
| Power | 50 W, 110/220–240 V auto-switching |
| Dimensions | 325 × 78 × 292 mm |
| OS / Firmware | MS-DOS 5.0 with Amstrad Desktop |
| Model no. | MEGAPC3H40 (system), PC14DSM (monitor) |
The Amstrad Mega PC is a 386SX IBM-compatible PC with Sega Mega Drive hardware on an ISA card, sold by Amstrad under licence from Sega. The PC side is Amstrad's PC7386SX: Amstrad's own service manual says the main CPU unit is the same as the PC7386SX and refers engineers to that machine's service manual for it, and covers only the games card and the PC14DSM monitor itself.[1][2] The system shipped with a 14-inch dual-sync colour monitor, the PC14DSM, which accepts both the PC's VGA output and the Mega Drive's lower-frequency picture.[1]
History
[edit | edit source]Sega Retro gives the UK launch as December 1992 at £999.99, citing Sega Pro and Sega Force, followed by releases in France, Italy, the Netherlands, Greece and Australia in 1993, and price cuts to £699, £599 and then £499 during 1993.[3] Wikipedia gives 1993 for the release, in PAL areas including Europe and Australia, and says the machine was discontinued in 1994.[4] A 486-based successor, the Mega Plus, was advertised; both sources doubt that it was released.[3][4]
Hardware
[edit | edit source]PC side
[edit | edit source]Amstrad's Mega PC specification lists a 25 MHz 80386SX, 1 MB of RAM expandable to 16 MB through four SIMM sockets, a 40 MB hard disc (28 ms), a 3.5-inch 1.44 MB floppy drive, two 16-bit ISA slots of which one holds the games card, and Super VGA with 256 KB of video memory, expandable to 512 KB.[1] The board has eight 30-pin SIMM positions, U2–U9, in four banks of two (H and L); on the Mega PC board photographed for Wikimedia Commons only banks 0 and 1 (U2–U5) carry sockets, and banks 2 and 3 are bare footprints.[2][5] The Mega PC parts list gives the main board as CPU PCB main 273894 and the power supply as 273888, the same part numbers as the PC7386SX's main PCB assembly and power supply module.[1][2]
| Ref | Part | Role on the schematic |
|---|---|---|
| U13 | 80386SX-25 | CPU |
| U14 | (socket) | 80387SX coprocessor position |
| U15 | WD76C10 | System controller, memory and bus control |
| U33 | WD76C20 | Floppy and IDE interface, real-time clock |
| U17 | WD76C30 | Serial, parallel and interrupt controller |
| U50 | WD90C11 | VGA controller |
| U51, U52 (U53, U54) | 44256 | Video RAM; U53 and U54 are the 512K option |
| U57 | ADV471 ("ADV471-66" in the parts list, "ADV471KP66" on schematic sheet 13/13); the photographed Mega PC board has an ADV476KP66E[5] | RAMDAC |
| U55 | ICS1394 | Video clock synthesiser |
| U32 | 8042 | Keyboard and mouse controller |
| U18, U19 | 27C512 | BIOS ROM, low and high |
The board drawn in the PC7386SX manual is silkscreened Amstrad VSC386SXD V.2.01, the same marking as a Mega PC board photographed for Wikimedia Commons.[2][5] Sega Retro describes the PC side as built on Western Digital's chipset, with feature-connector pads, an unused PC-speaker position and other unfitted parts on the board.[3]
Mega Drive side
[edit | edit source]The games card plugs into the ISA riser and carries the Mega Drive hardware and the PC's AdLib-compatible sound. Its parts list includes a Motorola MC68HC000FN8 (U18), a Z80 (Z0840004PSC, U13), a Sega 315-5487 (U12), a Yamaha YM3812 FM operator (U3) and YM3014B DAC (U6), two NJM2070M amplifiers (U31, U32), and a 53.2034 MHz crystal (U15).[1] Amstrad's specification gives the Mega mode processor as an 8 MHz 68000; Wikipedia gives 7.14 MHz.[1][4]
Amstrad's daughter board circuit shows a PC/Sega mode switch (SW2), the reset switch (SW1), a cartridge detector switch (SW3) and the dual volume control (VR1).[1] Sega Retro says the slider on the front must be moved to one side to open the cartridge slot and control pad sockets and to the other to use the floppy drive, that the PC can keep running in the background while the Mega Drive is in use, and that the Mega Drive side is not region-locked.[3]
Connectors
[edit | edit source]Amstrad lists a parallel port, two RS-232C serial ports, PS/2 keyboard and mouse sockets, an external VGA monitor port and a monitor power socket, a PC analogue joystick port, two Sega-compatible control pad ports, the Mega Drive cartridge slot, a Mega CD compatible connector and a stereo headphone socket.[1] Video from both sides leaves through the same 15-pin VGA connector; Sega Retro and Wikipedia say that the Mega Drive picture stays at 15 kHz, so a monitor must sync at both 15 and 31 kHz.[3][4]
Power
[edit | edit source]The rating label on the rear gives an input of 100–240 V AC, 3 A, 50–60 Hz, and outputs of +12 V 2 A, +5 V 7.5 A, −12 V 0.2 A and −5 V 0.1 A, with a switched AC outlet for the monitor rated at 1 A.[6] The supply is a module, replaced as one part.[1][2]
Repair guides
[edit | edit source]- Amstrad Mega PC Maintenance Guide – opening the case, the backup battery, memory and video RAM, the monitor adjustments
- Amstrad Mega PC Troubleshooting Guide – supply rails, the mode switch and monitor sync, cartridge and keyboard faults
- Amstrad Mega PC Capacitor Replacement Guide – electrolytics on the main board and in the PC14DSM monitor
Documentation
[edit | edit source]- Amstrad Mega PC Service Manual – the games card and the PC14DSM monitor
- Amstrad PC7386SX Service Manual – the main board, power supply and case shared with the PC7386SX
Related pages
[edit | edit source]- Sega Mega Drive / Genesis (Model 1)
- CRT Discharge Procedure · Capacitor Failure Symptoms · Hard Drive Maintenance and Repair
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Amstrad plc, MEGAPC3H40 with Games Card / PC14DSM 14" Dual Synch Colour Monitor Service Manual. Hosted as File:Amstrad Mega PC Service Manual.pdf, described at Amstrad Mega PC Service Manual. Specification (PDF p. 2); note to engineers (p. 3); MEGAPC3H40 cabinet, IC and miscellaneous parts lists (p. 4); exploded view (p. 5); daughter board circuit (p. 7); PC14DSM alignment procedure (p. 25) and parts lists (pp. 31–32).
- ↑ 2.0 2.1 2.2 2.3 2.4 Amstrad plc, PC7386SX Personal Colour Computer Service Manual, first published October 1992. Hosted as File:Amstrad PC7386SX Service Manual.pdf, described at Amstrad PC7386SX Service Manual. Technical specification and safety tests p. 2; main PCB top view p. 3; schematic diagrams 1/13–13/13 pp. 5–17; cabinet exploded view p. 18; parts lists p. 19.
- ↑ 3.0 3.1 3.2 3.3 3.4 Sega Retro, "MegaPC". Retrieved 2026-10-02. Launch date and prices with their magazine sources, the front slider, the Western Digital chipset, the VRAM upgrade and the Mega Plus.
- ↑ 4.0 4.1 4.2 4.3 Wikipedia, "Amstrad Mega PC". Retrieved 2026-10-02. Release in 1993, the £999.99 price, discontinuation in 1994, the ISA card and riser, the ports, and the unreleased Mega Plus.
- ↑ 5.0 5.1 5.2 Mister rf, "Amstrad VSC386SXD V2.01.jpg", Wikimedia Commons, 2022 (CC BY-SA 4.0). Retrieved 2026-10-02. A Mega PC main board marked VSC386SXD V2.01, with its chipset and the blue cylindrical battery.
- ↑ Bungle, "MegaPC Rear.jpg", Wikimedia Commons, 2007 (public domain). Retrieved 2026-10-02. Rear panel and rating label of a Mega PC (model MEGAPC 386SX).
