The Electron is a great little micro and it's amazing what can be done with it. However, nothing is perfect and it has its faults.

Apart from being a bit slow, the Electron is also rather short on memory. The BBC Micro is much better off, being both faster and - when using the very memory efficient teletext Mode 7 - having around 7K more RAM free.

The memory available on the Electron is further decreased when using high resolution and multicolour graphics modes. And in Mode 0 with a Acorn Plus 3 (which also grabs a huge chunk of RAM), you can just about fit a program in to print your name on the screen!

Admittedly I'm exaggerating, but the problem is there. Now Slogger has put an end to the days of "No Room" and "Bad MODE" with its Master Ram Board. This provides the Electron with a staggering 28K of memory in any screen mode and a few other goodies besides. But first of all, how's it done?

The Master Ram Board adds 32K of Shadow RAM and is essentially the same as found in the BBC B+.

The Operating System is patched and the Electron uses this extra RAM rather than the built-in memory for your programs. What this means is that the micro doesn't use any of the memory allocated for your program to store the screen display.

So HIMEM is set to &8000 regardless of mode and whatever the Operating System needs for the screen is taken from the built-in RAM. There are both advantages and disadvantages to this system, as we'll see later.

An additional bonus is that Slogger's Turbo Driver is built-in with the Shadow RAM. This speeds up the Electron by as much as 300 per cent depending on the screen mode.

When it's on you can't access the Shadow RAM butit is useful for speeding up games and breathes new life into old software. You'll find a full review of this in the July 1986 issue of Electron User.

The Master Ram Board is fitted by Slogger; simply post your Electron to them and back it comes with the only visible change being a small three-way toggle switch on the left of the case.

This can be used at any time, even with the machine turned on, to change the operating mode of the Electron. However, doing so crashes the computer and CTRL and BREAK is needed to reset the micro. This is quite normal.

The positioning of the switch gave rise to a small criticism of the board, in that I was working with the Electron on a crowded desk when it suddenly froze up.

Nothing at all wrong with the board, I'd just knocked something against the switch and accidentally changed the operating mode.

In the first position the Electron behaves as normal, in the second the Shadow RAM is switched in and in the third the Turbo and is switched on.

With the switch in normal mode there is nothing untoward noticeable. The Electron acts as it always has.

Switching to Shadow mode and pressing CTRL-BREAK produces the start up message Acorn Electron 64K. HIMEM in all screen modes is then &8000 giving a maximum of 28K of RAM free. The extra memory can be used by word processors, databases, spreadsheets, languages and so on.

For instance, word processors could have text files of up to 28K resident in memory and use either 40 or 80 column screen modes.

All legally written software will work but programs which use illegal methods - such as directly accessing the screen memory - will not run.

In both Turbo and Shadow RAM modes there is quite a significant increase in performance. Table 1 shows the timings for some simple programs running on the BBC Micro, standard Electron and Electron in either Shadow or Turbo mode - the speed is the same.

Test 1 was run in Mode 6 and calculated and printed the SIN, COS and TAN of the numbers 0 to 100. Test 2 was Test 1 carried out in Mode 0 to see the effect of changing mode.

Test 3 dimensioned and filled 1,000 element array in Mode 6, and Test 4 did the same in Mode 0. Finally, Test 5 drew 100 random triangles in Mode 2.

As can be seen, as well as adding extra memory, Shadow mode also speeds up the Electron and is directly comparable to the BBC Micro.

In addition, there are no significant variations in the execution time of programs running in different modes, unlike the standard Electron.

The days of changing to Mode 6 to do your number crunching, then back to Mode 2 to display the results, are gone with the Slogger Master Ram Board.

In Shadow Mode, the Electron's built-in RAM is used for the screen display while your program is in Shadow RAM. Of course, the screen memory doesn't take up all 32K of RAM and the built-in RAM that isn't being used for the screen from address 0 up to the screen start is free for your use. It can be used as a Printer Buffer or for data storage for instance.

This memory will be at least 12K and its actual size depends on the screen mode selected. With Mode 0, there is 12K to play with and with other modes that consume less RAM, there can be up to 20K free.

BASIC can't make use of this extra memory, except indirectly. Access is by a new Operating System Call which allows you to read or write to it.

The fact that programs run in Shadow RAM and that the screen memory is in the old Electron RAM gives rise to the one unavoidable drawback with most Shadow RAM systems, not just this one.

Programs that access the screen memory directly will not work in Shadow RAM. So for some games you''ll need to run the Slogger board in either Turbo or normal Electron mode.

The Slogger board will give you more space and extra speed, but won't turn your Electron into a BBC Micro.

Finally, the board provides a new Operating System ROM replacing the old. This has the same legal entry points as the Electron OS, and adds the new OS call mentioned above.

On the whole I liked it very much. It's a good piece of equipment which will no doubt find much use. The increase in speed provided by the Shadow RAM will also be extremely valuable and the additional feature of the Turbo mode for speeding up games is great. I can thoroughly recommend it.

Joe Pritchard