The Master RAM Board, as Slogger have christened their Electron add-on, is a two-in-one product: Shadow RAM, and speed-up board. The latter feature may be familiar to readers of Electron Computing (in previous A&B issues). We fitted our own Turbo Board earlier this year and reported its ability to speed up a variety of games and graphics-based programs. Games like Aviator and graphics like A&B's Global View programs benefit greatly.

The 32K Shadow RAM provided by the Master RAM Board is *fast RAM*, but many games cannot access this additional RAM because of the way they have been written. To incorporate the Turbo feature was an inspired move and makes the Master RAM Board an especially high performance add-on, applicable to all sorts of users.

Most exciting for serious users off the Electron is the shadow feature. The extra RAM is available to *correctly written* software. This includes firmware such as Slogger's own Starword, View and Viewsheet.

For instance, Viewsheet with tape gives 20,494 bytes free; with ADFS it has 16,654 bytes free; with shadow enabled this becomes 28,686 bytes free.

The figures for Starword, tape and ADFS are: 12,542 and 8,702. This becomes 25,086 with shadow enabled. Note that Starword is working in 80 column mode throughout.

There are the figures for the Acornsoft View cartridge:

View with ADFS: 16,894 bytes free
View with tape: 20,734 bytes free
View with Master RAM Board: 28,926 bytes free

As with the comparable BBC Micro systems, there is 28K available for data, text or Basic program files. The screen Mode makes no difference to available memory when Shadow RAM is switched on. Thus the eight colour and hi-res graphics screen Modes can equally be used in Basic programs without cramping the programmer's style with memory restrictions.

Because of the need for both shadow mode and Turbo speed (without the associated problems with games which POKE directly to the screen), Slogger has supplied a switchable system. The switch located towards the rear of the left hand side of the Electron has three positions: for normal Electron operation, Turbo and Shadow. This hardware switching is clean cut and, we imagine, less awkward than trying to do it in software through keyboard presses or * commands. The scren message:

Electron 64K

indicates that shadow mode is on.

Acorn Electron TURBO

indicates Turbo mode.

In order to provide Shadow RAM for the Electron Slogger has had to rewrite the Operating System. The new Slogger MOS (Machine Operating System) is automatically paged in when Shadow Mode is selected. The new bank of 32K becomes main memory as far as software is concerned.

When an instruction is encountered which should result in a value being written to a location in the screen memory, e.g. Basic PLOT or VDU, screen memory is *engaged* and the value sent on its way again, the instruction is chanelled to the correct piece of hardware.

If you take a look at the Electron memory map you'll see that there is a spare 12K even when the Shadow RAM is providing 20K screen memory. When screen Modes which use less memory are active, then even more memory is available to the user via a JuMP address within the Slogger MOS. Full technical details are given in the documentation and the obvious application which comes to mind for this spare RAM is a print buffer.

A Starword user, for instance, could enable the buffer and send a complete text to it for printing. Once the text is in the buffer, the user can return to wordprocessing or load and use another program. Meanwhile, the printer continues with the text.

More memory but also more speed: but how much? This is the listing of Test 1 which we used to test the speed of the Master RAM board:

10 MODE 1
20 TIME=0
30 FOR I%=0 TO 20480 STEP 4:I%!&3000=&55AA55AA:NEXT
40 PRINT TIME
50 END

The results were:

Time for test 1 with Master RAM board switched to Normal: 2760
Time for test 1 with Master RAM board switched to Turbo: 880
Time for test 1 with Master RAM board switched to Shadow: 854

To summarise, with Shadow RAM activated, any software which directly accesses screen RAM (&3000-&7FFF) does not work but all other legally written software does.

Shadow considerably increases the memory available for programs. Any programs previously too large to work on an Electron with Plus 3, such as A&B Computing's Olde English Font and Adventurescape's Xanadu, can now be accommodated.

In Turbo mode, as well as games and graphics performing much faster, input/output activity, such as a printer dump, is also speeded up.

Games, of course, are great with Turbo, Repton 3 works fast and smooth! See our review next month of the Electron version.

An interesting side effect on our Electron with Plus 3 and Plus 1 and other add-ons connected (an extreme case!) was the weakened sound generation. It's the first to go when the machine is pushed.

On the compatibility side, Plus 3, Plus 1 and Advanced Computer Products Sideways RAM all work in all modes. The Slogger T2P3 did not work in either Turbo or Shadow mode.

We tested the board as much as possible but we are always interested in hearing from owners with other peripherals so that we can pass on information to other Electron owners about compatibility and suitability. Drop us a line if you have any comment.

The Master RAM Board has made a great impression in our brief acquaintance, successfully boosting the Electron both in terms of memory and speed. A great little combination.