Amstrad's 6128: Battering RAM

128K micro + disc + monitor + CP/M = 300! Exclusive Your Computer review by Simon Beesley of the machine that should have Commodore and Sinclair quaking in their shoes.

The Amstrad 464 was launched in June last year at about the same time as the bug-free QLs began to hit the streets. 15 months later only 60,000 QLs have been sold while the Amstrad has established itself as one of the three bestselling home computers in Britain. How is it that in a year when almost every other micro manufacturer folded or floundered, Amstrad has flourished?
Undoubtedly one reason is that the 464 comes with a monitor and built-in cassette recorder at an unprecedently low price. But equally important is the fact that, although its design is not especially advanced, it scores highly in almost every department - graphics, sound, Basic, construction, and I/O connections.
This computer is largely free of the quirks and ommissions that flaw most other micros: a tacky keyboard on the Spectrum, antiquated Basic on the CBM-64, bugs on the QL and Oric, the memory-starved BBC, and so on.
Amstrad followed the 464 with the 664, which has a built-in 3in. disc drive in place of the cassette recorder. It has a few extra Basic commands such as the graphics command Fill, and sacrifices 1,280 bytes Ram to the disc operating system. But its major difference is the ability to run CP/M 2.2, which is supplied partly on disc and partly on Rom. The idea behind providing CP/M is to widen the machine's scope for attracting business users.
Just a few months after the launch of the 664, the company has now produced another computer with a built-in disc drive, the 6128. This comes with a total 128K Ram and runs an enhanced version of CP/M 2.2, CP/M Plus. It is still software compatible with the earlier models.
Although the 6128 offers more than the 664 - which will be quietly dropped from production - it costs less: 299 with a monochrome monitor, 399 with a colour monitor. If you are not fussy about picture quality you can buy a 30 modulator and use the monochrome unit with a colour TV.
Originally Amstrad announced that the 6128 was solely for the American market. It is not hard to guess why the company has delayed the announcement of the machine's U.K. launch until the last minute. But it is tough if you have just spent 449 on a 664. In appearance the 6128 is more or less the same as the 664. Amstrad has sensibly repositioned the cursor keys at the front of the keyboard and the overall height has been reduced. At the back there is the same array of ports as on the earlier model - a Centronics-style printer interface, an expansion port, and a socket for a second disk drive. Also unchanged at the side are the cassette and joystick ports together with a stereo jack for sound output.

Apart from the addition of CP/M Plus and another 64K Ram the machine's specification is the same as the 664's. Based around a Z-80A processor running at 4Mhz, it carries 128K Ram and 48K Rom. The Basic interpreter and the operating system are held in 32K of the Rom, while the remaining 16K contains Amsdos and a small part of CP/M. Amsdos is Amstrad's own disc operating system which serves as an alternative to CP/M.

The two systems coexist peacefully, reflecting the 6128's dual nature both as a small business machine and a home computer. Basic is switched out when CP/M is running so you cannot then load or save Basic programs. If you are using Amsdos you need to run CP/Mto format discs, back up and copy files; otherwise you can ignore it.

When Amsdos was first introduced Amstrad described it as a fast cassette system. You might expect a disc operating system to be rather more than this.