A review of the Acorn Archimedes.
Published in The Micro User, August 1987.



HAIL Archimedes, the world's fastest micro.
Acorn has jumped back onto centre stage of the computer scene with a family of micros that seems destined to keep the company in the spotlight for years to come.
It has taken a dramatic leap from the world of 8-bit – by-passing the hotly contested 16-bit market – to top the bill in the as yet to be explored wonderful world of 32-bit.
Just as the Acorn's backroom boys provided the company with a relatively unassailable lead – at the time – with the first BBC Micro, so they've done it again with the Archimedes.
And they've even managed to edge out mighty IBM in the finishing straight in the 32-bit stakes.
Most of the credit must go to Acorn's research and development team – and the strong nerves of the top management who backed them.
For whereas it was the brilliance of the backroom boys who helped develop the revolutionary Risc chip on which Archimedes is based, it was the Acorn executives who kept on bankrolling them even during financially troubled times.

EUREKA!
Archimedes, the world's
fastest micro, has finally
arrived. We tell you all
you want to know about
Acorn's wonder machine

The end result, however, will reap dividends for years to come.
Archimedes – like the BBC Micro – is a machine ahead of its time. Or rather a family of machines, with successive generations – each one more powerful than the other – to be released over the next few years.
Such is the technology within that even the first models to be unveiled – the A300 series – are faster than any micros ever seen before.
And the power is still almost untapped. For the Risc chip's performance is currently limited only by the Memc chip, the memory controller which can only handle up to 4Mb for the time being.

A mind-boggling array of advanced features to be found in Archimedes – a 4,096 colour palette with a possible [256] colours on screen at any time, eight channel stereo sound, WIMPs and anti-aliasing, which smooths out the block-like structure of conventional computer graphics. Yet it still retains definite links with its famous predecessor, the BBC Micro.
Whereas there are 21 screen modes, eight are the same as the BBC Micro. And the operating system, Arthur, supports all the old familiar *FX calls together with numerous extensions and entirely new ones.
Acorn has even developed software to allow Archimedes to emulate the BBC Micro's 6502 processor.
It is a machine for the future that hasn't forgotten its roots.
·A team from The Micro User has already met Archimedes – their words and pictures can be found on the next few pages.


WIDE RANGE OF OPTIONS

THE first of the Archimedes family of super micros to be launched is the A300 series.
As the entry level machines, these will go on sale in September under the BBC label.
They will soon be followed by the more expensive and expandable A400 series – provisionally priced from £1,400 to £2,500 – which will carry the Acorn badge.
On the A300 front, there will be two models to choose from – the A305 and the A310, priced from £799.
The A305 offers 0.5 Mb of ram – expandable to 1 Mb – a 1 Mb floppy, 512k of rom and red function keys, while the A310 has 1 Mb of ram.
Both 300 models can be expanded by adding another 1 Mb floppy or 20 Mb Winchester, a two socket backplane and podules – Acorn's way of describing peripheral modules.

The A400 series will arrive in the form of the top of the range A440 starting at 4 Mb in November, priced at around £2,500.
It will be joined in the first quarter of 1988 by the A410 costing in the region of £1,400. This model is offered with 1 Mb but can be expanded to 4 Mb.
Substantial discounts are to be offered on volume purchases of all machines for education.
Features common to both series – apart from the 32-bit Risc chips – are that they are 3.5in floppy machines with dramatic sound capabilities – eight separate stereo channels – as well as stunning graphics, offering up to 4,096 colours.

Each consists of a three box system, a small computer unit (similar in size to the new IBM PS/2), enhanced IBM style keyboard with mouse, choice of monitor options, a BBC style operating system (Arthur), BBC Basic V including Basic Editor, ADFS [Advanced Disk Filing System], window environment in rom with Desktop Manager, 6502 Emulator, printer/ serial/ monitor/ stereo sound interfaces, Econet [local area network] plug-in option, capability of accepting podules (plug-in cards) including I/O, rom and Midi.
Monitor options offered by Acorn itself are a 12 in monochrome white screen or a 14in medium resolution colour monitor to show off the 256 colours.
The A400 series – when it arrives – will support much higher resolution on special monitors.
And as for the A500? That's waiting in the wings and is likely to take the form of a scientific workstation.


PALETTE

One of the great attractions of the Archimedes is the analogue colour palette which allows any pixel on the screen to be displayed as one of 4,096 different colours.
The original BBC Micro has a digital palette that can be accessed with the VDU19 command. In effect this means that any pixel on the screen can be displayed as any one of eight different colours. This expands to 16 if you regard "flashing" as a colour.
But have you ever wondered what the extra zeros are for on the end of the VDU19 statement? They are to extend it to control the analogue palette. With the original BBC Micro any one of the three guns on the TV display can be on or off. With the Archimedes each gun can be made to vary its intensity.
In fact there are 16 different levels of brightness that can be produced by each of the red, green and blue guns in the monitor. This enables you to mix the three guns in varying proportions, producing subtle shading and colours.
No longer do programmers have to stick to the gaudy primary and secondary colours. Now a whole host of golds, browns and steel blues become possible.
This should mean a great improvement in the appearance of graphics and pictures, with shading and shadows effectively portrayed as well as more meaningful colours for particular applications.

Archimedes System

Colour palette demoGraphic games
Amazing effects can be created with Archimedes's superb graphicsFractals and games take on a new look with Archimedes

GRAPHICS

THE first thing that really stands out on the Archimedes is the graphics – there are 21 modes as seen in Table I.
The first eight exactly match the old BBC Micro modes to allow software to transfer easily to the new machine. Mode 7 on the BBC Micro is implemented with special hardware whereas on the Archimedes it is simulated.
This is possible due to the great speed of the Risc chip. With at least half a megabyte of memory in the machine even the most memory-hungry modes do not take up an excessive amount of memory.
Of major interest are modes 10, 13 and 15 which allow eight bits to be assigned to each pixel giving a total of 256 different colours on the screen at the same time. This can be used for shading or complex palette-switching animation effects, enabling stunning graphics to be created.
The graphics commands implemented are very much the same as the old BBC Micro coupled with Acorn graphics extension commands – in fact similar to those found in the Master. Acorn forward planning has ensured that most of the commands have unused parts that are now fleshed out.
These include predefined shapes, patterning and rapid flood fill effects. Coupled with the speed of the Risc chip, these allow effects created using Basic that were previously only possible with convoluted machine code.
The very high resolution modes 18, 19 and 20 will require a special multi-sync monitor. The reason for this is that the normal TV standard can't cope with so many horizontal lines.

ModeResolutionColoursTextRam Use

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
640x256
320x256
160x256
n/a
320x256
160x256
n/a
Teletext
640x256
320x256
160x256
n/a
640x256
320x256
n/a
640x256
n/a
n/a
2
4
16
2
2
4
2
Teletext
4
16
256
4
16
256
16
256
16
16
80x32
40x32
20x32
80x25
40x32
20x32
40x25
40x25
80x32
40x32
20x32
80x25
80x32
40x32
80x25
80x32
132x32
132x25
20k
20k
40k
40k
20k
20k
20k
80k
40k
40k
80k
40k
80k
80k
80k
160k
132k
132k
Also for multi-sync monitors:
18
19
20
640x512
640x512
640x512
2
4
16
80x64
80x64
80x64
40k
80k
160k
Table I: Arthur screen modes

SOUND

THE sound system is quite complex. It can do far more than just mimic the equivalent commands on the BBC Micro, and brings new heights of sophistication to built-in computer sound systems.
There can be up to eight channels assigned to the system and each can be located within a stereo position. The values controlling this range from 1, fully left through 128, centre stage, to 255 fully right.
There is a built-in loudspeaker and a rear jack socket for connection to an external speaker of hi-fi system. The volume can be controlled logarithmically or linearly.
The sound can be derived from waveform look-up tables making it possible to simulate a wide variety of musical and not-so-musical sounds. These are disc based and loaded into memory when required.
This means you are not stuck with the sounds that were developed before the Archimedes was launched. There should be a steadily growing library of instrumental and other sounds available and also programs that allow you to develop your own.

In addition, speech and real sampled sound can be produced. Imagine a game where the jet fighters roaring towards you sound just like the real thing.
Most of the handling of the sound outputs is performed by direct memory access from the peripheral chips, so the amount of processing time that sound generation demands is normally quite low. This will allow complex sounds to be generated while the processor is getting on with something else.
There is even a tuning control on the output to enable the Archimedes to be tuned to the same pitch as real instruments.
The sound buffers can be anything from 16 bytes to 4k and the sample rate from 1µs to 32µs per channel. As there can be up to eight channels this will give an overall sample rate of between 125kHz to 4kHz. This allows you to go from basic telephone quality to very good quality indeed.


Archimedes keyboard
The keyboard layout showing some of the new keys

PODULES

A PODULE is a plug-in card allowing all sorts of additional items to be connected to Archimedes. Any interfacing circuits can be built on these Eurocard size boards and slotted into the computer.
Each podule has its own small panel so the line of the computer is not spoiled, reducing the risk of developing "spaghetti" hardware with all sorts of modules and wires being connected.
Some versions of the Archimedes will have space for two podules and others room for four. In fact the software can support more than this so don't be surprised to see podule extension boards on the market before very long.
There are basically four types of podule that can be used:

Simple podules: These will provide simple input/output to the Archimedes and use a separate 16-bit I/O data bus controlled by the I/O controller chip.

Perhaps the most important will be the one that emulates the user port, 1MHz bus and analogue port of the BBC Micro. Others will be for connecting things like a teletext adapter, modem or video digitiser.

Memc podules: These can occupy up to 8k of address space and can be accessed much faster than the simple podules. They are intended for interfaces using large memory maps, a prime example being a sideways rom podule.
Many sideways roms can be installed on the same podule which would occupy pages in the BBC Micro.

Co-processor podules: While all other podules use a 64-way direct connector, this one uses a 96-way connector, to allow full access to the 32-bit data bus. It is designed to be used by processors that will share the workload of the Risc chip. Note that the same term was used to describe the second processors on the Master but here it is quite different.

It could be used by a floating point co-processor to speed up arithmetic operations or by other Risc chips. As Risc chips are designed to work together it is possible in the future to develop multiprocessor machines with this podule. Normally only one podule slot will be able to have a co-processor connected to it.

External podules: These are fitted outside the main machine and can have up to 32k of address space devoted to them, allowing you to have circuits that are physically too large to be fitted internally into the Archimedes.
All podules must identify themselves to the computer by a series of machine readable locations. This will normally be implemented in a small fuse link prom.
Acorn expects podule manufacturers to register with them to obtain a unique manufacturer's identification number to be placed in this space. Undoubtedly there will be people who will not play by these rules, but those who do can expect to have no trouble with podule compatibility.


Back panel of Archimedes
The back of the main unit showing the sockets


WIMPS

ARCHIMEDES contains a complete WIMP management system in the Arthur Operating System. The computer is so fast that the whole desktop environment on the Welcome disc is written in Basic using the Window Manager. Using the facilities you can create windows and icons, move the windows around, rescale them and remove them. A window can lie over or under any other.
Mouse access is just as simple, and you can define up to four different pointers (a simple pointer, a busy-bee symbol or anything else). You can also change the size of the pointer at will. The whole system is very flexible and every serious software producer or user should make use of it.

Archimedes logo

ARTHUR

THE Arthur Operating System consists mainly of passive routines called by user programs to perform the many operations such as reading the next key from the keyboard, putting a letter on the screen and so on.
Because of the amazing capabilities of the Archimedes, each one of these apparently simple operations can in fact be tremendously complex. You, as the user, will never see all the details of how pressing the letter X at the keyboard produces a highly ornate X one inch high on the screen.
All the standard BBC Micro entries into the operating system, for instance oswrch or osfile, have been preserved and operate exactly as before. The VDU commands 0-31 are basically unchanged – but some have been extended to take into account the power of the new machine.
VDU17 (COLOUR) and VDU18 (GCOL) now allow 256 colours and colour tints. VDU23 has all the facilities introduced in the Master plus other Archimedes special effects: for example VDU23,17,5 | swaps the foreground and background colours, giving the inverse video effect.

The Command Line Interpreter, the part of the operating system which deals with star commands, has undergone the most dramatic changes. In the BBC Micro all the CLI does is recognise (or not) a command and pass it round the roms and filing systems to see if it is a valid command.
The Arthur CLI performs the same function on a superficial level – but there is much more to it. Output from the command (for example the list of files from *CAT) can be re-directed to a text file and if a command requires input then it can be taken from a file. You can have string and number variables and there is a *IF statement. The following example produces a catalogue:
*SET FRED "HELLO"
*IF FRED="HELLO" THEN CAT

New osword commands are available to control such things as the mouse and the screen base address.

The standard filing system provided is the ADFS with many enhancements. Since the Archimedes has a built-in 3.5in drive, discs can be swapped directly from the Compact, or any other BBC Micro (or Electron) using 3.5in drive and ADFS.
The packaged interrupt handling in the form of events is still available. In fact only event 3, analogue conversion complete, is not available. There are no joysticks because you have the mouse instead.
There is no sideways rom facility, but this is not necessary when you have a potential of 64Mb.
Even with 0.5Mb in the basic model you have twice the memory available in a fully expanded BBC Micro (16 sideways roms of 16k each, plus the other 48k).
However you add your own software modules, which are equivalent to the sideways rams, so language and service software can be added to your machine dynamically.


BASIC V

To describe the new version of BBC Basic and its programming environment as boring is not an insult – it's a compliment to the skill of the writers in keeping to their specification.
Because so much in the Archimedes is improved and different, the Basic had to stay the same so people would feel at home. Rest assured that typing a program into the Archimedes looks and feels the same as using a BBC Micro.
But when you get down to the commands provided, Basic V is anything but boring. Table II provides a list of most of the new ones.

But of course complete upward compatibility is provided. If you have written a program in BBC Basic that only uses standard commands, including operating system commands like osword, then that program will run, with no modifications required. If you have it stored on 3.5in ADFS disc you can plug in and just chain it.
The two commands INSTALL and LIBRARY allow you to load procedure and function libraries into memory and access them from the program without having to write them afresh each time. There is also an APPEND command if you want to combine two programs.

In the area of mathematics you can now do matrix calculations in one command, pass arrays into procedures and functions and dimension local arrays. Also both value and variable parameters can be passed into procedures.
Something not mentioned in the User Guide is the fact that Basic V has an assembler for the ARM (Acorn Risc Machine). So watch The Micro User for a full rundown on programming in ARM code.
We hope we've succeeded in conveying our excitement about this very worthy successor to the BBC Micro.
The Archimedes's incredible speed and its breathtaking hi-res graphics and sound – coupled with the high degree of compatibility with the BBC Micro – puts all its competitors to shame.


Control Statements

IF <condition> THEN
  <multi-line statements>
 ELSE
  <multi-line statements>
 ENDIF
WHILE <condition>
  <multi-line statements>
 ENDWHILE
CASE <expression> OF
 WHEN <list of expressions>
    :<statements>
 <lots of WHEN statements>
 OTHERWISE <statements>
 ENDCASE

Graphics

MOVE [BY] x,y
DRAW [BY] x,y
POINT [BY] x,y
FILL x,y
LINE x1,y1,x2,y2
RECTANGLE [FILL] <coordinates>
CIRCLE [FILL] <coordinates>
ELIPSE [FILL] <coordinates>
ORIGIN
WAIT
MOUSE ON/OFF
MOUSE TO
MOUSE STEP
MOUSE RECTANGLE
MOUSE COLOUR

Error Trapping and Debugging

ON ERROR LOCAL
LOCAL ERROR
RESTORE ERROR
ERROR <number>,<string>
REPORT$ (pseudo variable)
TRACE STEP
TRACE PROC

Sound

SOUND ON/OFF
VOICES
STEREO
BEAT
BEATS
TEMPO

Miscellaneous

List variables       LVAR
Assign to part of LEFT$()=,MID$()=
strings and RIGHT$()=
Get line from file =GET$#
Exchange variables SWAP
Total array elements =SUM
Shift numbers left <<<
and right >>>
Find size of array =DIM
Find current mode =MODE
Call system routine SYS

Table II: Some new Basic V instructions

Archimedes logo
Bitmapped text
Conventional
Anti-aliased text
New

The diagram left shows how a character is displayed on screen by a conventional micro. However, the Archimedes uses a technique called anti-aliasing to smooth out the rough edges by assigning shades of grey to adjacent pixels (see the diagram above right).
The increased readability of the fonts means that you can get up to 132 characters a line – a boon for word processing.
Additionally, there are two types of fonts which can be defined: A simple font (defined on an eight by eight grid) and a large font, which can be any size. It shouldn't be long before software houses like AMS develop a host of new fonts for you to use.




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