Amstrad CPC464

(expanded to CPC 6128 spec.)

Owner: David Cantrell
Location: Bexhill-on-sea, Sussex, England

A classic from England! I'll let owner David Cantrell take it from here:

This is the very first model of computer manufactured by Amstrad. It was powered by a Zilog Z80 processor clocked at 4MHz, with 64K RAM, 32K ROM containing the OS and BASIC, and with a built-in cassette drive. The BASIC, written by Locomotive Software, was VERY powerful, allowing the BASIC programmer to manipulate up to 8 windows (with their own text streams) at a time, file I/O, direct access to operating system functions, setting up of interrupts and timers, with their 'payloads' written in either BASIC or machine code, 3 channel stereo sound, and graphics.

It came with a choice of either a colour or monochrome green screen monitor, which also contained the power supply. Prices when introduced in 1984 were (I think) UKP300 for the greeny screeny, and UKP400 for the colour model.

Later models replaced the tape with a 3" disk (CPC 664) and also upgraded the memory to 128K (CPC 6128) as well as fixing a few minor bugs in the OS and BASIC ROMs.

Popular add-ons were additional RAM packs, up to a total of 576K, 3" disk drives for the 464, second drives (usually 5.25" or 3.5"), and add-on ROMs. Many commercial programs were distributed on tape, disk, or ROM. The machine supports up to 250 add-on ROMs (although the power supply would give up before then :-)

Machines fitted with disk drives were supplied with CP/M system disks, as were add-on drives for the 464. The 464 and 664 had CP/M 2.2 supplied, the 6128 was supplied with CP/M+ (CP/M 3.1?) which could use the extra banks of memory, allowing up to 61K TPA.

My own machine started life as a bog-standard CPC 464, but has had the OS/BASIC ROM replaced with a CPC 6128's; an additional 64K RAM pack for a total of 128K; a ROM box containing Protext word processor, BCPL (grandfather of the C programming language), Maxam assembler, and Utopia (general purpose utilities); a DDI-1 disk interface, which contains the AMSDOS and CP/M bootstrap ROM; a FD-1 3" drive; and a 3.5" second drive. After all that, as far as software is concerned, it's the same as a CPC 6128 with a lot of extensions.

Other less common add-ons included a serial interface (there wasn't one as standard), an 8-bit printer port (the built-in one was 7-bit - weird!), disk/CPM ROM replacements, scanners, TV tuners for the monitor, UHF modulators allowing the use of a normal TV instead of the monitor, peer-to-peer networks, and hard disks.

This machine still works perfectly, and apart from the ROM upgrade has never had a single part replaced. It gets used occasionally, for playing games, transferring software for use with an emulator, and mainly for nostalgia.

I also know of at least 4 machines locally which are in daily use in small businesses, used for word processing and databases.

Amstrad's codename for the 464 during development was `Arnold', a name which appears in the ROMs of all versions; but ever since upgrading her to 6128 spec, I've called mine Ariadne.

In addition to the great description above, David was also kind enough to provide loads of pictures, complete with descriptions:

Here's a list of the pictures, and a brief description of each. They were taken on a table in my work room, which gave me more room for maneuvre. The machine normally sits on my desk right next to the PC, but I felt that it ought to stand alone for these pictures.
  • 3" disks as used by the CPC range. The one on the left is a CP/M+ system disk, the middle one is a CP/M 2.2 system disk, and the one on the right is an unused disk. That unused disk alone is a museum piece in its own right! These are flippy disks, storing up to 180K on each side with the standard formats, although special formatting software could squeeze an amazing 213K on each side! The disks are incredibly robust. Some of mine have survived dust, damp, heat, freezing, and being used as frisbees.
  • CPC464, as it was when first taken out of the box. Notice that it has a cassette deck on the right of the keyboard, and not a disk drive. Later versions had a disk drive here. The numeric keypad could have up to 36 functions programmed into it. When powered up, pressing CTRL-ENTER (the blue ENTER key on the keypad) would load whatever was on the tape.
  • 464 with just a few of the available add-ons - 3" and 3.5" disk drives on the right, with the interface hanging off the back; a 64K RAM expansion pack between the computer and the disk interface; and a ROM-box to the left behind the keyboard, connected to the same expansion bus as the disk interface and RAM pack.
  • The same setup as above, showing the tangle of cables which resulted from using all the toys at once. It would have helped if the cables were longer, but the bus logic chips couldn't drive the signals reliably any further. Notice the 64K RAM pack sitting nice and snug against the back of the machine, and everything else dangling in space. This is because the RAM-pack had a pass-through for the expansion bus, the ROM-box connected with a cable hanging off a pass-through, and the disk interface had no pass-through, despite it being produced by Amstrad and breaking their own design guidelines.
  • The inside of the ROM-box. This one's loaded up with 4 expansion ROMs, out of a possible 8 in this box. They are Protext (word processor), Maxam (macro assembler), BCPL (the grand-daddy of C), and Utopia (general-purpose utilities). The edge connector on the right is to enable you to add another ROM-box - and another, and another, and so on. The one on the left is for a 'RAMROM', a 16K RAM chip which can be 'blown' and used as a ROM - heavily used in writing and debugging ROM-based software.
  • The manuals for the CPC464 and the DDI-1 disk interface. The DDI-1 manual also contains a cut-down CP/M 2.2 manual, but isn't much use for serious CP/M use - to encourage people to buy Amstrad's expensive reprint of the full manual!
  • A not-very-clear picture of the back of the CPC 464, attempting to show the expansion ports. They are (from left to right) stereo jack, RGB, 5V DC input, expansion bus edge connector, Centronics edge connector, 9-pin D-sub digital joystick connector.
  • The startup screen of an unexpanded CPC 6128.
  • Startup screen of the same 6128, but with tons of add-on ROMs.

As if all the above wasn't enough, David also supplied Amstrad contacts on the net:

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