Multiface | Code Like It's 198x

The Multiface was a box with a red button. Plug it into the back of a ZX Spectrum, load a game, and at any moment a press of the button stopped the game dead and put a menu along the bottom of the screen. From there you could save the whole running program to tape, Microdrive or disk, look at any byte of memory and change it, then carry on playing as if nothing had happened. Romantic Robot, a London company, advertised it in November 1985 as “the essential Spectrum companion”, for £39.95.

That one button did several jobs. It moved tape games to faster storage, and it let players stop a game and carry on later. It also turned the Spectrum’s memory into something an owner could inspect, which made it a favourite of cheat-finders. The same abilities made it an efficient copying machine, and Romantic Robot spent the rest of the decade explaining that it was not meant to be one.

What the first Multiface did

Romantic Robot’s first advertisements sold the Multiface One as “all three in one compact box”:

a “push-button back-up facility of any program to cartridge, disk, wafer, tape”;
a joystick interface;
a composite video output.

Franco Frey tested it for CRASH in March 1986. The joystick interface was Kempston compatible, “port mapped to address 31”, so it worked with the many games written for the Kempston standard. The video output was of less use: it was taken straight from the Spectrum’s edge connector, and some Spectrums put no usable signal there.

The button was the point. “The save facility is obtained by pressing the red button,” Frey wrote. “This can be done at any time, regardless of the program running.” The menu offered EXIT, RETURN, SAVE and POKE, and SAVE could store either a screen or the whole program. The Multiface compressed what it saved, leaving out empty memory, so that, in Frey’s test, a typical 16K program took about 13K on a Beta disk and loaded within ten seconds. The saved copy came in four parts: a BASIC loader, the main code, the screen and what Frey called “the operating code”.

How it froze a program

The trick depends on a feature of the Spectrum’s Z80 processor. The Z80 has two kinds of interrupt. The ordinary one can be switched off by a program, and games often switch it off. The non-maskable interrupt (NMI) cannot: when an add-on pulls the NMI line low, the Z80 finishes its current instruction and jumps to address $0066, whatever the program is doing. The Spectrum brings the NMI line out to its expansion connector for add-ons to use.

The Spectrum’s own ROM was no help. Its routine at $0066 was meant to pass the NMI on to an address of the programmer’s choice, but a bug means it can only jump to address zero, which resets the machine. Chris Smith, in his book on the Spectrum’s ULA, describes how add-on makers got round it: “by disabling the ZX Spectrum ROM and enabling their own in its place whenever they activate the /NMI signal.” The Multiface did exactly that. It carried 8K of ROM for its program and 8K of RAM to work in, and when the button was pressed it switched them in where the Spectrum ROM normally sits, at the bottom of the address map. The NMI then landed in the Multiface’s code rather than a reset. Because its memory sat where the Spectrum ROM normally was, the Multiface took “NO part of SPECTRUM RAM”, as the advertising put it, and could save every byte of the game. Returning to the game switched the Spectrum’s ROM back in.

Frey found one limit. RETURN went straight back to the frozen program. EXIT left both the Multiface and the program, so that the program could be studied, altered or customised, “but only on the condition that the computer doesn’t crash on exit, which depends on the existence of standard system variables”.

The family

Model	First advertised	For	Price at launch
Multiface One	October 1985	48K Spectrum, or a later model in 48K mode	£39.95
Multiface Two	late 1986	Amstrad CPC	£46.95
Multiface 128	early 1987	“any Spectrum”, 48K and 128K	£44.95
Multiface 3	autumn 1987	Spectrum +3	£44.95; £49.95 with a through port

Romantic Robot’s advertising set the One and the 128 side by side: the One “works on any Spectrum but in 48K mode only” and “has a built-in joystick interface (Kempston)”, while the 128 “works on any Spectrum - 48K and 128K”.

The Multiface 3 was built for Amstrad’s disk-drive Spectrum. Rupert Goodwins reviewed it for Sinclair User in November 1987. For a +3 owner with a shelf of tape games, he wrote, “the only way you’ll get your software on disc is via the Multiface”. It could also look through all of the +3’s 128K, “not just the 48K’s worth that Basic has access to”, and let a +3 in 48K mode keep using its disk drive. “I’m not giving mine back without a fight,” he wrote.

For the Amstrad CPC, the Multiface Two did the same job, and Romantic Robot’s advertising quoted Amstrad Action calling it “the cleverest hardware device at present”.

Genie and the hackers

Romantic Robot sold software that ran inside the Multiface’s own 8K of RAM. The most important was Genie, a disassembler that loaded into the Multiface or the Multiprint printer interface. The advertisement put it plainly: “load ANY program, RUN it, STOP it when you wish and let GENIE disassemble it”. Genie could also dump memory to a printer, search for text and opcodes, and view and alter memory and the Z80 registers. It cost £9.95, and Romantic Robot called it “solid gold for hackers”.

This is how the Multiface fed the magazines’ cheat pages. A frozen game could be searched for the byte holding the number of lives, and the byte changed. Once someone had found the right address, anyone with a Multiface could use it. Your Sinclair’s tips pages printed two kinds of cheat side by side. One was a BASIC listing to type in and run before loading the game. The other was a short list of addresses and values under the heading “Multiface Pokes”, such as three addresses set to zero for infinite lives, to be typed in at the Multiface’s POKE prompt after freezing the game. See POKE culture for how that habit grew.

Backups, copies and the law

A device that could save any running program could copy any program, and Romantic Robot’s advertising changed its line on this more than once. The first advertisements, in 1985, said the Multiface was “designed to remain attached to RUN programs it saved as it is meant only for personal use in accordance with copyright laws”. Frey’s review four months later found that “in most cases MULTIFACE ONE need not be present to reload the programs it has been used to save”. By late 1987 the advertisements said “programs saved with MULTIFACE run on their own (except hyper tape back-ups)”.

The Multiface 3 went back the other way. Goodwins explained why. “Software houses are stuffy about this,” he wrote, since “they can see games being copied and distributed by pirates”. “Romantic Robot is sensitive to this, and claims that any program saved using a Multiface 3 will only load back with the machine attached.”

The Copyright, Designs and Patents Act 1988 changed the tone again. In June 1989 Romantic Robot’s advertisement in Your Sinclair opened: “Because of possible implications of the coming new Copyright Act the MULTIFACE may soon be NO LONGER SOLD in the UK. This is YOUR LAST CHANCE to buy the ESSENTIAL SPECTRUM ADD-ON.” It took £10 off every model, bringing the Multiface One to £29.95. Prices had already been falling: the One was £39.95 in September 1988 and £34.95 by April 1989.

The Multiface did not disappear. Your Sinclair was still printing “Multiface POKEs” in its tips pages in the 1990s, and Sinclair User was still carrying them in 1992.

Sources

Your Computer, October 1985, p. 22: Romantic Robot advertisement (Multiface One, £39.95).
CRASH issue 22, November 1985, p. 103, and Your Spectrum issue 20, November 1985: Romantic Robot advertisement (Multiface One, £39.95; features; “designed to remain attached to RUN programs it saved”).
CRASH issue 26, March 1986, p. 86: Franco Frey, Multiface One review (Kempston port 31; the video output; the red button and menu; compression and the four-part save; 8K ROM and 8K RAM; the system-variables caveat; reloading without the Multiface).
CRASH issue 34, November 1986: Tech Tips (Genie, “a disassembler package for Romantic Robot’s Multiface 1”).
Amstrad Action issue 16, January 1987, and issue 18, March 1987: Romantic Robot advertisements (Multiface Two, £46.95; “the cleverest hardware device at present”).
AMTIX issue 13, November 1986: Multiface Two news and review.
Sinclair User issue 60, March 1987: Romantic Robot order form (Multiface 128 at £44.95, Multiface One at £39.95, Genie at £9.95).
CRASH issue 45, October 1987, and issue 46, November 1987, p. 96: Romantic Robot advertisements (8K ROM and 8K RAM, “NO part of SPECTRUM RAM”; the One and 128 compared; “programs saved with MULTIFACE run on their own”; Genie; Multiface 3 at £44.95).
Sinclair User issue 68, November 1987: Rupert Goodwins, Multiface 3 review (£49.95 with through port; the quotations above).
Your Sinclair issue 25, January 1988, p. 8: Romantic Robot advertisement (“MULTIFACE 3 for Spectrum+ 3, MULTIFACE 128 for any other Spectrum, MULTIFACE 1 for 48K Spectrum”).
Your Sinclair issue 33, September 1988, p. 65, and issue 40, April 1989, p. 60: Romantic Robot order forms (prices).
Your Sinclair issue 34, October 1988: tips pages (“Multiface Pokes”).
Your Sinclair issue 42, June 1989, p. 66: Romantic Robot advertisement (the Copyright Act; £10 off; Multiface One £29.95).
Sinclair User issue 125, July 1992: readers’ Multiface POKEs.
Chris Smith, The ZX Spectrum ULA: How to Design a Microcomputer (ZX Design and Media), chapter 21, p. 224: the NMI on the expansion port, the bug in the ROM routine at $0066, and how peripherals switch in their own ROM.
Adrian Dickens, Spectrum Hardware Manual (Melbourne House, second edition): the Z80 accepts an NMI at the end of its current instruction and jumps to address 66 hex; the NMI line on the edge connector.