In the Master Emulation ROM (MER) review last month I mentioned MER's use of Solidisk's RTC. What about this product? Does it make a good investment when bought alone? What would it give you?

With a (rather meagre) manual, the RTC is supplied as a small board about 1.5" x 3" which plugs into a vacant ROM socket (plug it in the one on the right on the BBC board and it will overhang the other three without interfering with them). It has a trailing connection to a Nicad PCB battery, which Solidisk suggest you can solder into position on the board if you have the headroom. The board contains an HD146818 Real Time Clock module, a 16K EPROM and some support circuitry.

Not only does it offer the user a normal *TIME function - and again TIME$ (Basic IV) and |D (View3), but also a full *CONFIGURE and *UNPLUG/*INSERT/*ROMS suite all by itself.

The RTC module, as in the Master, contains 50 bytes, but the exact meaning of each of these bytes is left to the software designer. Dabs Press wisely chose the same meanings as Acorn's Master, but Solidisk have not. This means that when disabling MER with *MODELB, RTC then takes over the configuration bytes, can't make sense of them and so reconfigures them to their item defaults. You must thus reconfigure them all over again. You could of course keep an EXEC file available for use with both systems, but one slight complication is that Solidisk's RTC expects *CONFIGURE FILE to be followed by the Filing System Number, as opposed to the Master's Filing System ROM Number. For a reason I don't understand, neither MER nor RTC is compatible with the PANEL options of Beebug's Master ROM either.

In addition to the above features, the RTC ROM also accepts star commands to make various types of alarm available. At a set time you can have a simple beep, print out the contents of a file or execute a command of up to 34 characters (held in CMOS RAM). These will occur even if other programs are running!

Finally, you have a command to leave a digital clock running at the top right of the screen as well as support for full low-level OSBYTE 161/162 and OSWORD 14/15 calls.

So what are your options? £30 for RTC, £15-£20 for MER, or both? That depends on what you are looking for. If it's secure ROM unplugging and configuration then RTC gives you that, plus a real time clock and alarm. But if you make frequent use of multiple filing systems then the temporary filing system of MER is a godsend. To buy both is expensive, and you are left with an unconfigured Beeb when you disable MER. It's your choice.

Product: Real Time Clock
Supplier: Solidisk Technology, 17 Sweyne Avenue, Southend-on-Sea, Essex SS2 6JQ.
Price: £29.00