Opus Discovery

The following advert was taken from Your Spectrum Issue18

THE NEW DISC DRIVE SENSATION

At last Spectrum owners can choose a TRUE disc drive system for their computer, backed by REAL software support and available with the most comprehensive specification yet developed.
For just £199.95 Discovery offers a new level of performance and a combination of advanced features which make other fast storage systems for the Spectrum and Spectrum + look obsolete.
No wonder one leading computer magazine, Sinclair User, recommended Discovery in its latest guide to fast storage systems for the Spectrum.

Discovery has been designed to take no USER RAM from the Spectrum during the use of tape
based programs, it accepts the same commands as 'Interface 1' allowing you to use many of the
cassette programs designed for microdrive and we've provided you with the firmware to use a
super-fast RAM DISC when you choose. Random access files are fully supported and formatting
and back-up routines are included in ROM.

Add to all this a range of great software titles on the latest 3.5inch disc cartrisges commissioned
by Boots and you begin to see why we named it Discovery.

Specifications:

250k 3.5inch disc dirve.
Video monitor output.
Joystick interface.
Peripheral through connector.
Parallel printer port.

The following review was taken from Advanced Home Computer

Sinclair Research has provided the Microdrive for the Spectrum, but a need has remained for a more reliable and accommodating disk drive system. We conclude our two part series on alternatives to the Sinclair Microdrive by examining the Discovery 1 from Opus, following our look at Rotronics' Wafadrive.

In the previous Hardware article we looked at the Rotronics wafadrive. Although this device proved to be
somewhat more reliable than the Microdrive, it turned out to be slower in comparison, and still based around
the rather suspect continuous tape system. In this article we turn our attention to a more conventional approach
to mass storage: a disk-based system from Opus Supplies.

A disk drive for the Spectrum does not represent a new idea. Over the past couple of years there have been a
number of disk operating systems and interfaces available for the machine; however, none of these systems have become particularly popular. This is partly because the interfaces have been advertised solely in the specialist press, which has given the devices an air of being intended only for the devout Spectrum enthusiast and machine code programmers, and partly because they have been available only through mail order houses and have not been given the kind of mass marketing needed to push them into the public consciousness.

The Discovery 1 is encased in sheet metal, extending the front of the machine to support the Spectrum that plugs into a cartridge slot via the expansion port. Although this seems a comparatively easy operation, users may find some difficulty in attaching the Discovery to the edge connector. This is because the cassette and aerial leads tend to get in the way and prevent the cartridge slot from being attached correctly. Bearing in mind that a badly attached edge connector could severely damage the Spectrum, this is a serious problem. The difficulty is not as pronounced with the original Spectrum (for which the Discovery was originally designed), but the new Spectrum +, with its larger casing, may have users struggling for several minutes before they are satisfied that the device is correctly fined. Once the Spectrum has been fitted to Discovery 1, the machine effectively blocks off the computers own power supply input. The Discovery has therefore been designed to power both itself and the Spectrum, thus making the micro's own external power supply redundant.

DUAL DRIVE UPGRADE

Above the cartridge slot on the left is a single 3.5inch disk drive, with space on the right for a second drive. (Opus intends to launch a dual drive version of the machine called the Discovery 2.) Discovery 1 users wishing to upgrade their systems to dual drive configurations can expect an external additional disk drive called Discovery + to be launched. However, users will not be limited only to Opus drives since the company claims that standard 5.25inch disk drives can also be added in the same manner.

In common with Rotronics, Opus's philosophy in designing the machine is to provide not only a mass storage
system for the Spectrum, but also to add extra peripheral interfaces allowing users to run printers and other devices.
A composite video monitor socket on the back of Discovery I has been provided, according to an Opus
spokesman, for business users wishing to attach a monochrome monitor (although of course composite video
does produce a colour signal) for lengthy periods of word processing. However, on a machine noted for its
colourful games programs, it is a pity that Opus could not have provided an RGB interface to produce a much
clearer picture.

On the right side of the Discovery is a single Kempston-compatible, Atari-standard joystick port, next to which is a bi-directional Centronics parallel printer port. Finally, there is a peripheral through connector to enable other
Spectrum-compatible interfaces, such as an RGB monitor, to be connected.

Like the Wafadrive, the Discovery disk operating system closely follows that of the Interface 1; for example,
issuing a command requires <GOMMAND> *. When the BASIC interpreter reaches the *, it does not recognise
it as being a BASIC command and attempts to generate a syntax error. However, the DOS intercepts it and
pages its own eight Kbyte operating system into the position of the lower eight Kbytes of the Spectrum's ROM,
and then interprets the command. It should be noted that if the user has made a syntax error, even the DOS
won't recognise it and an error message will be generated, although this will still be via the DOS ROM.

In designing its DOS system, Opus has gone further than Rotronics in providing Compatibility - all of the
commands available to the Microdrive have been retained. There are several reasons for this. Because of the
Spectrum's single keyword entry system, it is obviously easier to write an operating system using inherent
commands, rather than going to the trouble of writing your own. This also means that users who are already
familiar with the Microdrive operating system will be able to use the Discovery immediately, since all the
syntax is the same. Furthermore, tinkering with an operating system can lead to all kinds of unforeseen
problems with the memory map. This means that programs compatible with Interface 1 may not necessarily
be compatible with your revamped operating system, a problem that has plagued many other third party
peripherals.

The way in which Opus has closely followed the Sinclair Microdrive command system is most noticeable when
looking at the way the streams have been organised. On the Spectrum, output channels are organised into 16
streams numbered 0 to 15. Three of these are set aside for the screen, keyboard and printer, the others are free for use by any other peripheral. In the Sinclair list of Interface 1 commands, there are a number of single
characters that open channels to specific devices; for example 'm' for Microdrive. The Discovery has adapted these to its own use, thus the command LOAD * ‘m';1;'name’ will work just as well on Discovery 1 as on a
Microdrive, although in this case 'm’ refers to the disk drive. However, for added convenience, Opus has adapted the command format so that ‘m' can be omitted, thereby shortening the somewhat long-winded Sinclair system.
Other commands have also been adapted. The character 't' in a command on the Microdrive opens a channel to
the RS232 interface, whereas on the Discovery it opens the channel to the parallel printer.

THE DISKS IN OPERATION

The disk drive supplied with the system uses the double-density Sony format 3.5inch disks that are becoming
increasingly popular on microcomputers. The disks themselves each have a total capacity of 250 Kbytes, which, when formatted, provide 180 Kbytes of available storage space. The disk operating system supports random access when searching for a file, which is considerably faster than the serial search methods used on some other disk systems. Also, there is no limit to the number of files that can be held on a disk, which can be important then one wishes to save a number of short files. If the directory is quickly filled, there may be a large amount of space on the disk that cannot be used.

When comparing the time it takes to SAVE and LOAD a file using the Discovery and Microdrive the former proved to be somewhat faster in actually finding a file but considerably slower in SAVEing and LOADing it. Finding a file is faster on the disk system because the files are organised by random access whereas the Microdrives, by their nature, are serial access devices. Why accessing a file into memory is much slower is more difficult to explain, but it is a fact that the transfer rate of the Discovery 1 is much slower than that of the Microdrives - 15 Kbaud compared to 19.2 Kbaud. The real advantage of the Discovery lies in having a mass storage system more robust than the Microdrive's, and a storage medium having a wider range of manufacturers to choose from.

Opus appears to have given some thought to the problematic aspect of software support for the Discovery.
Obviously having a large company like Boots selling the product in their chain of stores is an advantage, since
software houses will be able to offer their products alongside the machine itself. The company has also
indicated that many software houses, including Melbourne House and Legend, have already agreed to transfer
some of their existing programs onto the 3.5inch disks.

The launch of the Discovery series of disk drives has clearly been well planned and Opus has obviously
attempted to provide its new line with as much chance of success as it possibly could. For the company,
the major task before it is convincing Spectrum owners that the Discovery is a more worthwhile investment
for their machine than the Sinclair alternative. If the time is right and the Spectrum owner is ready for a
disk-based system, Opus and its Discovery 1 could well be a success.