TIMEX DISC DRIVES ARRIVE

The latest in the growing number of disc systems for the Spectrum has been launched recently by Timex (Portugal) Ltd.

It offers the use of up to four drives, each of which can access up to 140K; only uses two bytes of Spectrum memory - unused ones in the system variables; has a very versatile filing system; features two, independent, RS232C ports and could, in theory, be used to run CP/M programs. It uses Hitachi 3in drives and the figures given relate to those, but 5.25 and 3.5in can also be used. On paper, at least, Timex is on to a winner.

The hardware is supplied in a number of separate, stackable, units. An interface, complete with a handy reset switch, plugs in the back of the Spectrum and is connected, via a cable, to the controller at the base of the stack. Onto that are placed the drives, and on top goes the mains power supply. Although the controller can handle four drives the power supply can only handle two, and so with a full complement of drives you will need two power supplies.

When formatted each disc has 160K of space per side and as the drives are single-sided the disc has to be turned over to access the other side. Of that 160K, 16K is taken up by the operating system and a further 4K by the directory leaving just 140K. On power up the operating system is transferred to memory in the controller leaving the Spectrum memory free.

One of the features rarely mentioned in these pages is the manual which accompanies most items of hardware. Some are good and some are not so good. The Timex manual is very bad.

The writer assumes a great deal of background knowledge about the system and therefore tells you what keys to press but not why you are pressing them.

To use the system all the normal load, save and merge commands are used, in the usual manner, including MERGE not auto-running.

The microdrive keywords are also used so CAT* will display the current directory; current in that you can have eight levels and up to 15 directories. Similar files can be kept in separate directories and directories can be kept in other directories.

The whole thing is arranged in the form of a tree. At the base, or root, are the two RS232 channels and the names of all the discs in the drives. Each disc name can hold a number of different directories and files, each directory can hold further files and directories, and so on up the tree.

As can be seen the directory structure is rather complex, possibly unnecessarily so on such a small machine with limited disc space. You can use just one level of directory which may make life easier.

The filing system offers two sorts of files. Both use the microdrive OPEN# and CLOSE# with the type defined using DIM. With the first sort strings are PRINTed to the file and can then be subsequently INPUT back into strings in the same sequence. The second sort is based on a record. That is a string of fixed length, up to 256 characters, which is PRINTed to the file as before. Up to a maximum of 65535 of such records can be sent to the file.

The system is supplied with a demo disc which contains, in addition to some simple Basic programs, utilities to make backup copies of discs, set an RS232 port to use LPRINT and LLIST, transmit and receive over the RS232 lines and dump a file to a printer in Hex.

The demo highlighted one of the problems with the system; because of the odd directory system it takes quite a time to discover how to load most of the programs. Once that is done it can be timed using the program:

10 for n= 1 TO 30
20 SAVE *"test" + STR$ n CODE 32000,200
30 NEXT n

SAVEing was a little slow at 1.16 minutes while loading and erasing were slightly better than average at 19 seconds and 23 seconds respectively.

All in all, Timex has produced a good system which is capable of doing most of the things you need from a disc. All it needs to do now is produce a manual which tells you how to use it.

Due to its complexities the price is high - £269 inc - but, in theory, if you change computer all you would need to change would be the interface, which should be quite cheap. The ability to run CP/M may also be useful but Timex will have to supply programs converted for the system.

The 3in discs used by the system are gaining popularity with home computer users but, with the drop in microdrive cartridge price, they are expensive at £4-£5. For further information on prices of add-on drives - expected to be around £100 - and power supplies contact Micro Interface on 01-340-0310.