|Company||Miles Gordon Technology|
|RAM||256 KB (internally upgradable to 512 KB, externally to 4 MB)|
|ROM||32 KB (boot code and SAM BASIC)|
|Text modes||32x24, 85x24|
|Graphic modes||256x192 (spectrum mode, 1 or 4 bits per pixel), 512x192 (2 bits per pixel)|
|Sound||Philips SAA1099 (6 channels, stereo FM synthesis, 8 octaves. MIDI interface build in|
The SAM Coupé (Pronounced: "Sam Koo-Pay" from its original British English branding) is an 8-bit British home computer that was first released in late 1989. It is commonly considered a clone of the Sinclair ZX Spectrum computer, since it features a compatible screen mode and emulated compatibility, and it was marketed as a logical upgrade from the Spectrum. It was originally manufactured by Miles Gordon Technology (MGT), based in Swansea in the United Kingdom.
The machine is based around a Z80B CPU clocked at 6 MHz, and contains an ASIC that is comparable to the Spectrum's ULA. Memory is accessible within the 64 KB range of the Z80B CPU by slicing it into 16 KB blocks and accessing IO ports to switch which blocks appeared in the 4 slots available to the CPU. The basic model has 256 KB of RAM, upgradable internally to 512 KB and externally with an additional 4 MB (added in 1 MB packs). The computer's primary storage medium is a cassette tape, though one or two 3.5 inch floppy disk drives can be installed internally as well. Six channel, 8 octave stereo sound is provided by a Philips SAA 1099 chip. The ASIC also includes a line triggered interrupt counter, allowing video effects to be synchronised to specific display positions with little effort.
The machine shipped with 32 KB of ROM containing code to boot the machine and a BASIC interpreter (SAM BASIC) 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 majority of disks shipped with SAMDOS, the system's first DOS, on them so that they could be directly booted. An improved replacement, MasterDOS, was also developed offering faster disk access, more files and support for the Real Time Clock for filestamps amongst many other improvements.
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 in between, very similar to the display lists of OpenGL, was provided.
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 led 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 disk for playback later without the Spectrum connected. The Messenger plugged into the Coupé's network port, and the Spectrum's expansion slot. Due to faulty break (NMI) buttons (needed to activate the Messenger software), a break-button card was also provided, which plugged into the Coupé's expansion slot.