One of the features supported by the Master but missing from the Compact, is a resident real-time clock and calendar. Permanent Memory Systems, the company which produces the desktop utility Genie, has recently released its answer in the form of a fully Master-compatible Compact Clock.

The device is supplied in a plain box with a five page instruction leaflet. To my surprise I found that the Real Time Clock, complete with resident software and battery backup, was no larger than a normal ROM mounted on a carrier board. Previous Real Time Clocks have required both the connection of the necessary hardware and the installation of a sideways ROM to operate the clock. PMS have combined these two devices into the same package.

The first paragraph of the instruction leaflet makes reference to the fact that the carrier board into which the ROM is plugged is known as a "Smart Socket" and contains both the RTC chip and its battery. The battery is not rechargeable but has a life expectancy of about ten years.

The fitting instructions are brief but to the point. Installation is no more complicated than inserting a normal ROM into one of the spare sideways ROM sockets. This should take no longer than about ten minutes and requires no technical skill or soldering. Once the device is fitted I would recommend that it is never removed for any reason as the legs are extremely flimsy and easily broken. It is surprising that a more durable base was not used.

Once in place, the Compact will accept exactly the same commands as would a Master for accessing the in-built Real Time Clock. Entering TIME$="Tue,19 Jan 1988.15:50:00" will set the date to the 19th January 1988 and the time to three fifty in the afternoon. The time is easily displayed with the *TIME command. As with the Master, the format of the date cannot be altered. The Compact Clock accommodates all legal methods of reading the Real Time Clock on the Master; even the Operating System calls OSWORD 14 and 15 are fully supported. This means that useful utilities such as the Date Stamping segment program for Wordwise Plus (published in Beebug Vol. 6 No. 6), will work without modification on a Compact.

Three further features increase the power of the PMS Real Time Clock considerably. The first allows the time to be displayed in the top right hand corner of the screen in either your own programs or in an application such as a word processor or spreadsheet. Unfortunately, although I have found this to work well with Wordwise and View, it did not work with Inter-Word and I would anticipate other problems with commercial programs.

There is also an alarm facility and a timer. Up to four alarms may be set at any one time and, providing that the machine is on when the time elapses, an audible alarm will be sounded for about ten seconds. The timer also allows an alarm to be set relative to present time. For instance, if your program includes a line *TIMER 00:01:30 the alarm will sound exactly one and a half minutes after that line is executed.

Although the PMS Real Time Clock supports all Acorn-approved methods of reading the Master Clock, this does not mean that all software will be able to use it. For example, any program which directly peeks into the CMOS RAM will fail in this way. Some programs, like Beebug's Master ROM, specifically ignore time and date facilities if the software determines it is running on a Compact. In addition, PMS have included a *NOALARM command which disables the clock display, alarms and timer, but does not clear the stored times.

One feature which I found disappointing was that the Real Time Clock Display enabled itself after a Ctrl-Break despite my having issued the *NOALARM command previously. I contacted PMS who assured me that this fault has been rectified and that the RTC will remain disabled after a hard reset.

The Compact Clock is a very clever device which is easily installed and operated. It provides a very useful Real Time Clock and is well documented. The price may seem high for the facility provided, though the technology is very much state-of-the-art. If you really do need a Real Time Clock on your Compact, then this device from PMS will fit the bill admirably.