IBM Personal Computer Model 5150

In normal use, it's doubtful you'd even notice it. The mono display adaptor, which occupies one of the expansion slots, doubles as a port for the Epson printer, so this will need a separate adaptor if you choose colour.

The standard device is the Epson MX-80 tractor feed with some soundproofing. The cable costs $55 extra [£30 at today's exchange rate]. The 'typamatic' keyboard is a work of art. Offering tactile feedback and automatic repeating on certain keys, it contains every key you could imagine using, all in a well-designed unit that owes a lot to IBM's experience in typewriter design.

It has 10 function keys, some assorted control keys and a separate numeric keypad that, when you toggle the NumLock key, accesses insert, delete, cursor, page up and down, home and end functions.

Tabbing can be both forward and backward, and a Prtscr key allows you to dump text from the screen to the printer. When programming in Basic, you can print most of the commonly used commands by hitting a single key with the Alt key depressed.
The 10 function keys are defined to give single-stroke facilities such as Save and Load, and you may redefine them by using the Key command in Basic. However, a mysterious key called Scroll Lock doesn't actually do anything.

The Benchtest systems each had two drives taking disks holding 160KB in 40 tracks of 8 x 512-byte sectors. Inside the System Unit is an 8088 processor which has an internal 16bit structure, 8bit data transfer and 20bit addressing capable of addressing up to 1MB of memory.

The 8bit data bus makes the 8088 compatible with the popular 8080/8085 support circuits. You get from 16KB to 256KB of RAM, plus 4KB or (with colour) 16KB of display memory on the adaptor card. Up to 64KB is held on the processor board and additional memory comes in 32KB or 64KB boards that plug into one of the expansion slots.

Other cards currently available are a game control adaptor and an asynchronous communications adaptor - an RS232C/current loop interface which can be driven between 50 and 9600 baud. Typically, a colour/graphics card takes one slot, the printer another, and the disk drives another. This leaves two slots free for games, communications and extra memory.

I'd say this package will suit 99.9 per cent of prospective purchasers' requirements. Microsoft's Cassette Basic interpreter, which takes up in 40KB of Rom with some I/O routines, comes as standard.

Enhancements and the Disk Operating System (DOS) are loaded from disk. Every peripheral is interrupt-driven, which means that when a particular device is not doing anything, it is ignored.

Once it has something to say, it interrupts the processor to demand attention. This makes programming much easier and also makes the machine run significantly faster by avoiding waiting time.

Our Benchmarks weren't designed to highlight this sort of activity so, although they're fast, they're not extraordinary. At switch-on the system runs its own internal diagnostic routines and beeps when it is ready for you to load programs or whatever.

It will also react to certain key combinations. For example, if you want to reboot the DOS, press Esc, Alt and Del [sic], while Ctrl with NumLock suspends program execution.