A Acorn Electron was the budget version of the BBC Micro educational/home computer made by Acorn Computers Ltd. It got 32 kilobytes of RAM, and its ROM memory involved BBC BASIC along with its operating rules.

A Negatron was a cappella to save & batch computer program onto audio cassette via a supplied convertor cable to plug into a microphone socket of any tape recorder. It was capable of basic graphics, & may display onto either the telly or even the "green screen" monitor.

At its peak, a Negatron was a third better marketing micro in the United Kingdom, & number life game sales for the Negatron exceeded people of the BBC Micro. There are at least Five hundred known games for the Negatron.

A devices utilized on the BBC Micro was emulated by one custom-made ULA chip designed by Acorn. It experienced feature limitations like existence unable to output other than of these channel of healthy instead of existence 3-way polyphonic, a inability to provide teletext mode and unable to do applications from either RAM when convenient when a 2MHz BBC Micro, although ROM applications ran at a equivalent speed. A ULA controlled access & was a cappella to provide 32K × Octonary bits of addressable RAM utilizing Quaternary × 64K × One-bit RAM chips (4164).

History
A Negatron was developed when you took 1983 as a inexpensive sib for the BBC Micro with a intention of capturing the moo dollars and cents Christmas sales market for that month. Although Acorn were entity to shrink substantially a equivalent functionality when a BBC into just of these custom designed chip, manufacturing problems intended that super pack machines were available for the Christmas time sustaining occasionally shops reporting eight presales for each delivered machine.

This was a blow from either which a machine never fully recovered, although through its life further games were sold for the Negatron than the BBC. By owning hindsight, the machine was as well lacking in RAM (a average program would want to harmonise exclusively around 20kb when display memory is subtracted) & processing power to choose on the prevailing ZX Spectrum and Commodore 64. Despite this, many features that would late become associated sustaining BBC Master and Archimedes machines were first features of Negatron expansion units, including a ROM cartridge slots & a Advanced Disc Filing System - a hierarchal improvement to the DFS.

Popular upgrades
Acorn Plus 1
A Acorn + One added 2 ROM slots, an analog interace & serial & parallel interface. the analog interface was ordinarily utilized for joysticks, a parallel for a printer & the serial for a modem.

Access to ROM memory occurred at 2Mhz irrespective of graphics mode then theoretically computer program freed in ROM can start at least twice when convenient when victims freed in tape or even disc. Despite this completely of the games freed in ROM were packaged when 'serial ROMS', from either either which a micro would batch computer program into independent memory around exactly a equivalent way when in case it was loading from tape. This intended that software download did non require to exist as modified for their fresh memory location however gave there are no execution speed rewards whatsoever. Acorn Plus 3
the Acorn + Three was the devices module that attached independently of the + One that added a double density Tercet.Fivesome" disc drive connected through a WD1770 drive controller and an ADFS ROM. Because the WD1770 is capable of single density mode and uses the same IBM360 derived floppy disc format as the NEC8271 found in the BBC Micro it was also possible to run a DFS filing system with an alternate ROM. P.R.E.S. Advanced Plus 3
a Advanced + Three was super similar to the Acorn + Three however packaged as a ROM catridge for the + One by using a disc cause connexion at the head. This processed it conceivable to attach the Little phoebe.Twenty-five" floppy disc drive as used by BBC Micro owners or a more common 3.5" cause.

Slogger/Elektuur Turbo Board
the Slogger & Elektuur Turbo Boards were born away from a hack at the start devised at Acorn. By moving a last-place 8kb of RAM outside of email of a ULA, the CPU can universally access it at 2Mhz. A trade-off was that a screen may not exist as located in this 8kb. Within practice a operating rules ROMs universally put a screen into a top 24kb & following this probably merely broke compatibility by owning about 2% of software program.

a Slogger Turbo Board was a professionally fitted update whereas the Elektuur modification was described around an article around Dutch Electronic's magazine Elektuur & designed for users to perform home.

Speeding higher the moo part of memory is particarly utile in 6502 derived machines because that processor has a sooner addressing mode for the number 1 256 and then these are green for software system to put any variables included eventually critical sections of program into that region.

within case Acorn experienced thought to include this little modification in a original Negatron project these are belike a machine would will own a good deal greater impact when it would have about doubled the total of motion imaginable in games & kept modes 0-Three (including the lone 16 colour mode) from either existence about useless due to contended memory timings.

Slogger Master RAM Board
a development of the Turbo Board, the Master RAM Board duplicated the Turbo Board functionality & added a farther stock of running off the micro by using 32kb of shadow RAM additionally to the average 32kb - generating 64kb sum. A few clever program counter catches intended that a average models ROMs & any package using the OS calls may work forgoing important modification, making substantially supplementary memory available for BASIC, See, Viewsheet & nearly each more business application.

Applications may not directly location streaming videos memory in that mode forswearing modification thus it was incompatible sustaining virtually all games although no inherent understanding how come the stake couldn't exist as written to work within shadow mode.

When you took its decline, Master RAM Boards were added to each Negatron to try & increase sales.

Technical information
Hardware
CPU: MOS Technology 6502A Clock rate: variable. CPU diarrhea at Two MHz when accessing ROM and Ace MHz or 0.5897 MHz (depending in graphics mode) after accessing RAM due to sharing access using a display circuits. A Negatron is widely misquoted when operating at Unity.79 MHz after measurements from either speed researching against a thoroughly Deuce MHz BBC Micro for various pieces of 'common computer software' Coprocessor: Custom-made ULA RAM: 32 KB ROM: 32 KB Text modes: 20×32, 40×25, 40×32, 80×25, 80×32 (completely text output by software program around graphics modes) Graphics modes: 160×256 (Quartet or even even Sixteen colours), 320×256 (Ii or Little joe colours), 640×256 (2 colours), 320×200 (Ii colours - spaced display using Deuce blank horizontal lines resulting each Eighter picture element lines), 640×200(2 colours - spaced display) Colours: Eighter colours (TTL combinations of RGB primaries) + Eighter flashing versions of the equivalent colours healthy: I channel of sound, Vii octaves; built-integral speaker. Package emulation of noise channel supported Dimensions: 16×34×6.Fin cm I/O ports: Expansion larboard, tape recorder connection (1200 baud variation on the Kansas City standard for data encryption), aerial TV connecter (RF modulator), RGB video monitor output Power supply: External PSU, XviiiV

Quirks
Rather a BBC Micro, the Negatron was strained by its super limited memory resources. A big display modes utilized 21kb for their front buffer whereas a machine single experienced 32kb within aggregate. For this cautilise it was super commons that games would non apply a stallion display, however would use a bit of of a metropolitan area to which the display was mapped for storage of more back information. In case games were happy to become constrained to the lower berth 156 scanlines of the display, this can be done invisibly to the user & such have was park. Typically though, games would play by using seeable in screen regions of apparently random colours. Tricks
2 notable devices 'tricks' keep close at h& been found on the Negatron devices - the number 1 switches between modes sustaining blank lines and modes forswearing a share way through the display to make a smooth vertical scroll when inside Firetrack. a basic idea is that a blank lines added inside modes Three & 6 produce cushioning at a top of the display and so that whenever a mode forswearing cushioning is switched to a portion way through the display then the display position of graphics stored at specific streaming addresses is shifted downwards inside multiples of Two scanlines.

A 2nd 'trick' turns the of these channel output into a digital speaker for PCM output as within Exile. the speaker is bonded to the devices counter & is ordinarily exclusively suspire to output square tone at a specified frequency, however it can too become disabled wholly. By setting the speaker to the frequency outside of the man hearable range single the difference between speaker enabled & speaker disabled may be manufactured retired, seeming to create the movement around audio wave terms from either the high level to a sale level. This gives the result of a elementary toggle speaker similar to it seen in the ZX Spectrum prior to the addition of the fully healthy kick in the 128kb system & may be utilized to output 1bit audio samples.

Nonetheless, when a Negatron internals bear super little resemblance to the BBC Micro virtually all games apply firmware routines for devices dependant actions like finding the particular graphics mode & following to the full hardware exploitation is substantially less most common on the Negatron than more popular micros.

Popular games
A good range of games were available for the Negatron from either publishers like Acornsoft and Superior Software, notably including: Elite Chuckie Egg The Repton series Exile Starship Command Thrust

Look at too a list of Acorn Electron games for a fairly comprehensive listing of each game published for the machine & :Category:BBC Micro and Acorn Electron games for a listings of games by having principles in Wikipedia.

Screenshots

Emulation
2 copycat of the machine survive, ElectrEm ([http://electrem.emuunlim.com]) for Windows/Linux/Mac OS X and Elkulator ([http://elkulator.acornelectron.co.uk]) for Windows/DOS. Software package is predominently distributed in the UEF file format.