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SAM_Coupé.jpg
The SAM Coupé was an 8-bit British home computer that was first released in late 1989. A popular misconception is that it is a clone of the Sinclair ZX Spectrum computer although it has a compatible screen mode and features that allows for emulation since it was marketed as a logical upgrade to the Spectrum. Originally manufactured by Miles Gordon Technology, plc. (MGT) based in Swansea in the United Kingdom.
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Hardware Overview
The machine was based around a Z80B CPU clocked at 6 MHz, and contained an ASIC that is comparable to the Spectrum's ULA. The basic model had 256kiB of RAM, (upgradable internally to 512kiB and externally to 4.5MiB), and used tapes or 3.5" discs for storage. Six channel stereo sound with digital sample support was provided by a Philips SAA 1099. The ASIC included a horizontal sync triggered interrupt counter.
Four graphics modes were provided:
- Mode 4 - 256x192, linear framebuffer, 4 bits per pixel (16 colours)
- Mode 3 - 512x192, linear framebuffer, 2 bits per pixel (4 colours)
- Mode 2 - 256x192, linear framebuffer, 1 bit per pixel with separate attributes, similar to the ZX Spectrum
- Mode 1 - 256x192, separate attributes, non-linear framebuffer arranged to match the display of the ZX Spectrum
In mode 1, extra wait states reduce the CPU speed by around 10% to give a more compatible running speed for ZX Spectrum software. The display can be disabled in modes 3 and 4, eliminating display memory contention for a full 6MHz running speed.
All modes are paletted, with a 16-entry CLUT selecting from a palette of 128 colours.
The machine shipped with 32kiB of ROM containing code to boot the machine and a BASIC interpreter written by Andrew Wright and heavily influenced by his earlier BETA Basic for the ZX Spectrum. No DOS was included in the ROMs, this was instead loaded from disk using the BOOT or BOOT 1 command, or the F9 key. The overwhelming majority of disks shipped with SAMDOS on them so that they could be directly booted and SAMDOS would automatically copy itself when a new disk was formatted.
The BASIC was very advanced and included code for sprite drawing and basic vector shapes such as lines and circles. The screen co-ordinate system for these was variable and could be arbitrarily scaled and centred. A provision for "recording" sequences of graphics commands so that they could later be repeated without the speed penalty of a BASIC interpreter inbetween, very similar to the display lists of OpenGL, was provided.
Video Memory Problems
The machine lacked a hardware scroll and could not blit the screen around fast enough for multicolour scrolling graphics.
All system memory was shared between the video output and the CPU, unlike on the ZX Spectrum which had large areas in which the screen could never be located. This incurred large speed penalties for all operations as the CPU was forced to wait for the ASIC when reading or writing to memory. Whereas the Spectrum display was 6912 bytes in size, the SAM's was 24kiB.
As a result the SAM Coupé's CPU ran only around 14% faster than that of the ZX Spectrum yet was expected to do four times as much work to produce the same amount of movement on the display.
Disk Drives
The SAM used Citizen 3.5" slimline drives which slotted in below the keyboard to provide front facing slots. Like IBM PC hard disks these contained not just the drives but also the drive controllers (WD1770 variants) with the effect that the SAM could run both drives simultaneously.
Expansion Ports
A large array of expansion ports were provided, including:
- Two internal drive bays
- SCART connector
- Euroconnector for general purpose hardware expansions
- Mouse socket (proprietary format, although a converter for Atari ST style mice was later available)
- Lightpen socket
- MIDI sockets
- Atari style 9pin joystick port
Uniquely the SAM's RF modulator was built into the power supply unit and connected via a joint power/TV socket. This made signal interference from the ACDC converter common and it was a popular but entirely unofficial modification to remove the modulator and keep it as a separate unit.
Kaleidoscope
The Kaleidoscope, announced by SAMCo shortly before bankruptcy, would have extended the machine's total colour palette to 32768 colours in such a way as to allow forwards and backwards compatibility by applications. Although complete the hardware disappeared with SAMCo.
ZX Spectrum Compatibility
Emulation of the ZX Spectrum was limited to the 48K and was achieved by loading a copy of the ZX Spectrum ROM and switching to display mode 1, which mimicked the ZX Spectrum display mode and approximated that machines processor speed.
The ROM was not supplied with the machine and had to be obtained from a real ZX Spectrum.
The 128K model's memory map was incompatible with the Coupé's memory model and the machine featured an entirely different sound generator. It was possible to convert games by hacking the 128K code.
Because the Coupé didn't run at exactly the same speed as the Spectrum even in emulation mode, many anti-piracy tape loaders would not work on the Coupé hardware. This lead to the development by MGT of a special hardware interface called The Messenger which could capture the state of a connected ZX Spectrum to SAM Coupé disc for playback later without the Spectrum connected.
Commercial Fortunes
MGT, Miles Gordon Technology, who launched the machine, went into receivership in June 1990, and the assets were mainly bought by a new company founded by Miles and Gordon called Sam Computers Ltd. The price of the SAM with floppy disk drive was brought down to under £200 and new games and hardware were released. SAMCo survived until 1992, and the remaining assets then were purchased by West Coast Computers.
Notable Software
The SAM Coupé was particularly notable for the wide array of disk based magazines that originated for it, include FRED and the official SAMCo Newsdisk. It also became notorious for the overwhelming number of puzzle games for the system, something that Spectrum magazine Your Sinclair referred to jokingly numerous times.
Several famous computer games were ported to the Sam, notably Manic Miner, Prince of Persia, and Lemmings. An unofficial but arcade perfect port of Defender surfaced late in the machine's lifespan.
Flash!
Flash!, an art package, was the only full application bundled with every SAM Coupé and as a result is probably the program best known to SAM owners. Written by Bo Jangeborg, author of the earlier ZX Spectrum program Artist II, it offered pixel editing in all four graphics modes, conversion of graphics from one mode to another and some basic animation functions.
Only full screen images were supported and the program's main flaw was an inability to view the entirety of an image while working on it.
A copy adapted for use with a mouse was bundled with the official mouse addon.
Software Houses
Before the machine was released US Gold infamously claimed that "[i]f, as with Strider, we've already produced a games across all common formats, all we have to do is simply take the code from the Speccy version and the graphics from the ST and sort of mix them together. This should take one bloke around two weeks at most."
Despite this, supporting the machine proved difficult and only a small number of software houses stepped forwards, most SAM specific.
Enigma Variations
An early supporter of the SAM, Engima published SAM versions of Defenders of the Earth, Escape From the Planet of the Robot Monsters, Five on a Treasure Island (based on Enid Blyton's Famous Five), Klax, Pipemania and SAM originals SAM Strikes Out (a Jet Set Willy influenced platformer) and Futureball (a Speedball influenced futuristic sporting title), Sphera (a mode 2 vertically scrolling shooter).
Revelation
The software arm of SAMCo, founded in 1992 due to the lack of support from mainstream publishing houses, was notable for publishing most of the SAM's best titles.
SAM original titles included Astroball, Batz 'n' Balls, Legend of Eshan, Sophistry and Wop Gamma.
SAM ports included Elite (nothing more than the 48kb ZX Spectrum version repackaged onto floppy disk), Prince of Persia, Manic Miner, Lemmings and Splat!.
FRED Publishing
Spun off from the disk based magazine, FRED Publishing were relatively late to the scene but supported the machine long after any of the other publishing houses. The jewel in their crown was the SAM conversion of Lemmings (and Oh No! More Lemmings), but they also published a number of SAM original titles such as Boing, Bulgulators, Dyzonium, Football League Manager, Impatience/Trilltex, Momentum, Parallax, Waterworks and the Witching Hour.
External links
- Sam Coupe Pro-Dos (CP/M 2.2) Resource Site (http://www.samcoupe-pro-dos.co.uk)
- SAM Coupe Scrapbook (http://www.mono.org/~unc/Coupe/)
- SAM Coupé.co.uk (http://www.sskardon.fsnet.co.uk/)
- SAM Coupé overview at Planet Sinclair (http://www.nvg.ntnu.no/sinclair/computers/clones/samcoupe.htm)
- SAM Coupé FTP archive (ftp://ftp.nvg.ntnu.no/pub/sam-coupe/)
- Quazar : Hardware, Software, Magazines and Repairs for the Sam Coupe (http://www.samcoupe.com/)
- SimCoupé - A SAM Coupé Emulator (http://www.simcoupe.org/)
- Spectrum Advanced Machine Website (http://sam.speccy.cz/)
- Dan's Coupe Pages, including FRED Magazine catalogue (http://www.podboy.demon.co.uk/coupe/)
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