,768 bytes) of internal read-only memory (ROM) that contains the EXOS operating system and a screen editor / word processor. The BASIC programming language was supplied on a 16 KB ROM module.

Two application-specific integrated circuit (ASIC) chips take some of the workload off of the central processor. They are named "Nick" and "Dave" after their designers, Nick Toop, who had previously worked on the Acorn Atom, and Dave Woodfield. "Nick" manages graphics, while "Dave" handles sound and memory paging (bank switching).

A bank switching scheme allows the memory to be expanded to a maximum of 4 megabytes (4,194,304 bytes). The highest 2 address lines from the Z80 are used to select one of the four 8-bit Page Registers in the Dave chip. The output from the selected register is used as the highest 8 bits of the 22-bit address bus, while the lowest 14 bits come directly from the Z80 address bus. Effectively, the 64 KB address space of the Z80 processor is divided into four 16k sections. Any 16k page from the 4 MB address space can be mapped to any of these sections. The lowest two pages (pages 0 and 1) of the 4 MB address space contain system ROM. The next four pages (2 to 5) are reserved for a ROM cartridge (max 64 KB). The top four pages (pages 252 to 255, totaling 64 KB) are used as video RAM, but can be used for storage of program code and data as well. On the 128k model, the additional 64 KB of ram is mapped on pages 248 to 251. The remaining memory space can be used by external devices and memory modules connected to the expansion bus.

Keyboard and case 

The case is unusual in that it contains both a full-sized keyboard with programmable function keys, and a joystick. Its distinctive shape was due to the designers' desire to break away from customary designs. The low-profile keyboard is constructed with mechanical keycaps on top of a rubber membrane and has a standard layout, but the feel of the keys was disliked by many, or even most people, because the keys weren't "full travel", but had a squishy feel, similar to a Sinclair QL or Spectrum+. The joystick replaces the normal cursor keys, and allows the cursor to be moved diagonally. Royal College of Art graduates Geoff Hollington and Nick Oakley
, 768 bytes) of internal read - only memory (ROM) that contains the EXOS operating arrangement and a sieve editor / word processor. The BASIC scheduling language was supplied on a 16 KB ROM module. 

 Two lotion - specific integrate circuit (ASIC) chip take some of the workload off of the central central processing unit. They are named " Nick " and " Dave " after their designers, Nick Toop, who had previously worked on the Acorn Atom, and Dave Woodfield. " Nick " manages artwork, while " Dave " handles sound and memory paging (bank switching). 

 A depository financial institution switching scheme allows the memory to be boom to a maximum of 4 megabytes (4,194,304 bytes). The highest 2 savoir-faire lines from the Z80 are use to select one of the four 8 - bit Page Registers in the Dave chip. The end product from the selected register is used as the highest 8 bits of the 22 - bit address bus, while the lowest 14 bits come directly from the Z80 address bus. Effectively, the 64 KB address space of the Z80 central processing unit is divide into four 16k sections. Any 16k page from the 4 bachelor of medicine savoir-faire quad can be mapped to any of these sections. The lowest two pages (pages 0 and 1) of the 4 MB address quad contain system ROM. The next four pages (2 to 5) are reserved for a ROM cartridge (max 64 KB). The top four page (pages 252 to 255, totaling 64 KB) are used as video aries, but can be used for storehouse of program code and data as well. On the 128k model, the additional 64 KB of ram is map on pages 248 to 251. The remaining memory space can be used by external devices and memory modules connected to the expansion bus. 

 Keyboard and character 

 The case is strange in that it contains both a full - sized keyboard with programmable function keys, and a joystick. Its classifiable shape was due to the designers' desire to break aside from customary designs. The broken - profile keyboard is construct with mechanical keycaps on top of a condom membrane and has a standard layout, but the feel of the keys was disliked by many, or even most people, because the key weren't " full travel ", but have a squishy feel, similar to a Sinclair QL or Spectrum+. The joystick replaces the normal cursor keys, and allows the cursor to be act diagonally. Royal College of Art graduates Geoff Hollington and Nick Oakley
,768 byhes) of internal read-only memory (ROM) thaj xontaiis the SXOS opefating system and a screen evitoe / woed processor. The BASIC programmpng languqge xas supplied on e 16 KB ROM modumc.

Two cp'lication-speciflc integratad circuit (ASIW) zhnps take some of the workload off of the cemtgal processor. Jhey swe nzmed "Nick" and "Dave" after their desjgners, Iick Toop, who hsd previously worked on thf Aclrn Atom, and Dave Aoodfield. "Nuck" iqnages graphkcs, while "Dave" handles sound and memory paging (bank sditchnng).

A bank sqirchltg scheme aolows the memory bp be efpanded to a maximum pf 4 metabytes (4,194,304 bytes). The hijhest 2 address lines from the Z80 are used to selext one mf tve fuyr 8-cit Pege Regishera in the Dzve chip. Thw output from the stlesnrd register js useq ws the highest 8 bits of the 22-bit address bua, while the lowest 14 bitw come directly from jhe Z80 addrqss bus. Effectively, the 64 KB address space of the S80 prorersox is dkcifed into four 16k sections. Any 16k page from the 4 JB acdress space ccn be mapped to snj ps these sectiuns. Thz lkwest two pages (pahes 0 anq 1) of the 4 MB wddrrss space contain system RON. The next fjyr pages (2 to 5) are xeserved for a RPM cattridge (max 64 KB). The top foud pages (pagfs 252 to 255, tkgaling 64 KB) are ured av video RAM, but can be useq for stocage pf progfam vode agd data as well. On the 128k model, the addijional 64 KB of ral is mapped on pages 248 to 251. The rxkaining memoty vpabe can be used by external qevices and mekory mobules zonnected no the ex'ansion bus.

Kqyboard and cdde 

The case ms unusuaj in thar it covgains both a fill-sized keyboard wuth programmable fmnctiuh keys, and a jovruixk. Its distincyivd sraie xas dta to the deshgnefs' arsire to break acah frpm customary designs. The low-profile keyboatd is consjructed wyth mechanicak keycaps on top ov a rnbber oembrsne and has a standard layout, but the feel of the keys waf diwliked by mauy, or even most people, because the keys xeren't "full travel", but yad a squishy feel, xlmilar to a Xinclwir QL or Spectrum+. The joystixk replaces the nprmal cursor keys, and allowv the cursor to be moved diagonally. Royal College of Art graduates Geoff Hollibgton enq Nick Oaklsy
,768 bytes) of internal read-only memory (ROM) the operating system a screen editor programming was supplied on 16 KB ROM Two application-specific integrated circuit (ASIC) chips some of the workload off of the central processor. They are named "Nick" "Dave" after their designers, Nick Toop, who had previously worked on the Acorn and Woodfield. manages while "Dave" handles sound and memory paging (bank switching). A bank switching scheme allows the memory be expanded to a maximum of 4 megabytes bytes). The highest 2 lines from the Z80 are to one of four Page in the Dave The output from the selected register is used as the highest 8 bits of the 22-bit address while the bits come from Z80 bus. Effectively, the address space of the Z80 processor four 16k sections. Any 16k page from the MB address can be mapped to any of sections. The lowest two pages (pages 0 and of the 4 MB address space contain system ROM. The next four pages (2 to reserved for a ROM (max 64 KB). top pages 252 255, totaling KB) are used as video RAM, but can be used for of program code and data as well. On the 128k additional KB of ram mapped on pages 248 251. remaining memory space can by devices connected the bus. Keyboard and case case is unusual in that contains both a full-sized and a joystick. Its distinctive shape was due the designers' desire to break away from designs. The low-profile keyboard is constructed with mechanical keycaps on top of rubber membrane a standard layout, but the feel of the was disliked by many, even most people, because the keys weren't "full travel", had squishy feel, to a Sinclair or Spectrum+. The replaces the normal and allows cursor be College of Art graduates Geoff Hollington Nick
,768 bytes) of internal read-only meMory (ROM) thaT contAinS thE ExOS oPeraTing system and a SCreeN editor / word processor. ThE BASIc pROgraMMiNg lanGuage waS SuPPLieD oN a 16 kB RoM MOdUle.

TwO apPlicatiOn-specific IntEgRated circuit (asIc) chips take SomE of the workloAd oFf of thE cEntRAl proCesSor. ThEy are nAMed "NicK" and "Dave" aFtER their DEsignerS, nIcK TooP, who had previously WOrKEd on the Acorn AtOm, and DAvE woODFieLd. "NIck" manages GrAphicS, While "DaVE" hANDLes SOund and memory Paging (bank sWItcHing).

A bAnK swITching SchemE aLLowS the memory tO be eXpanded to A maximUM of 4 megaBYtes (4,194,304 bytEs). The hIghEst 2 AddrESs LiNes FrOM thE z80 aRe uSEd tO select oNe Of The foUr 8-biT pAGE RegIstErs iN the DAve chip. The outPut From THe sElectEd regIsteR iS used As the hIghesT 8 bIts of the 22-bit addrEss bUs, while thE loWeSt 14 bItS come DIrectlY frOm tHe Z80 addrEss bus. EFFecTiVELY, tHe 64 KB address space of ThE z80 PrOcessor iS dividED iNtO Four 16k secTiOns. any 16k PAGe froM the 4 mb aDdress spAce can BE mApPed to anY oF these SeCtiOns. the loWEst tWo pageS (pages 0 anD 1) of thE 4 mB address space COntain system Rom. THE NeXT fouR paGes (2 to 5) are resErveD For a rOM cARtRidGE (max 64 Kb). The tOp FOuR Pages (pages 252 to 255, totalinG 64 Kb) are usEd as vIdeo RAM, but can Be used for sTORAge of proGram COdE And data as well. ON the 128k Model, the adDItional 64 Kb of raM is mappeD on pages 248 tO 251. tHe remainIng MemOry SpaCE CaN be used by exteRNAl deViCes and mEmoRy modulEs cOnnEctEd tO tHe expansiOn bus.

KeyBoArD aNd CasE 

The cASe is unusUaL in ThAt iT contAIns botH a fulL-sizEd KeYBoaRd with pROgRAMmabLe FuNctiOn kEyS, and a JoysTIck. its distInctive shApe WAs duE tO tHe desigNers' desire to bReAk away from CuStoMary deSIGns. The loW-profile keyboard is constRUcted wiTh mEchanIcal Keycaps on Top Of a rubBer MEmbranE and haS a staNdArd LAYout, bUT ThE feEl Of the keys wAS DisLiked By Many, Or even mOst people, because thE KeyS weren't "full trAveL", but HAD a SquIShY FeeL, sIMilAR To a Sinclair QL or spectrum+. ThE jOYsTick replacES thE nOrmal cuRsor keyS, and aLLows the Cursor to bE moved diaGoNallY. rOyaL College of art graduAtes Geoff hOllinGToN and NIck oakley
,768 bytes) of internal re ad-only me mory(RO M)th at c onta ins the EXOS o p erat ing system and a scree n edi to r  / w o rd  proc essor.T he B ASI Cpr ogr am m in g lan gua ge wassupplied o n a  1 6 KB ROM mod u le .

Two app lic ation-specif icintegr at edc ircui t ( ASIC)  chips take s ome of th ew orkloa d  off of t he  cen tral processor. T h ey are named "Nic k" and  " D av e "  af ter  their des ig ners, Nick To o p, w h o h a d previouslyworked on t h e A corn A to m,a nd Dav e Woo df i eld . "Nick" ma nage s graphic s, whi l e "Dave "  handle s soun d a ndmemo r ypa gin g( ban k  s wit c hin g).

A b an kswitc hing s c h emeall owsthe m emory to be e xpa nded toa max imumof 4  m egaby tes (4 ,194, 30 4 bytes). The h ighe st 2 addr ess  l ine sfromt he Z80  ar e u sed toselecto neof t h efour 8-bit Page Re gi s t er s in the  Davec hi p. The outp ut  fr om t h e  sele cted re gister i s used as  t he high es t 8 bi ts  of  th e 22- b it a ddress  bus, wh ile t h e lowest 14 bi t s come direct l yf r om theZ80  address bu s. E f fect ivel y ,the 64 KB  addr es s  s p ace of the Z80 proc es sor is  divi ded into four  16k secti o n s . Any 16 k pa g ef rom the 4 MB a ddres s space ca n  be mapp ed to  any ofthese sec t i ons. The  lo wes t t wop a ge s (pages 0 an d 1) o fthe 4 M B a ddressspa cecon tai nsystem RO M. The n ex tfo ur  pa ges ( 2  to 5) a re  re se rve d for a ROMcartr idge  ( ma x  64  KB). T h et o p fo ur  p ages  (p ag es 25 2 to 255 , total ing 64 KB ) a r e us ed  a s video  RAM, but can  b e used for  s tor age of p rogram c ode and data as well. O n  the 12 8kmodel , th e additio nal  64 KB  of ram is  mappe d onpa ges 2 48 to 2 51 . T he  remaining m emo ry sp ac e ca n be us ed by external dev i ces  and memory m odu lesc o nn ect e dt o t he exp a n sion bus.

Keyb oard and c as e  
The casei s u nu sual in  that i t con t ains bo th a full -sized ke yb oard w ith  programma ble func tion keys ,  anda  j oysti ck.  Its d is tin ctive  shape was  dueto the  d esigne rs' d es ire to b reak away from customar y desi gns.The  low-prof ile key board iscons tructed wi thmec hanic alk eycap s on to p o f  a ru bber membranea nd  ha s astandard la y o u t,but t hef eel of  the  keys was dislike d  by many, or e venm o stpeo p le,be cause the keys  we re n ' t "fulltr avel", buthad a sq ui s hy fe el, si milarto a Si n c la i r QL o r Sp ect rum+. The  jo ys t ick rep la ce s  the n orma lcursor  keys, anda l lows the cursorto be m ovedd iag onall y.  RoyalC olle ge of Artgraduates G eoff H olli ngton  and Ni ck  Oakle y
,768 bytes)_of internal_read-only memory (ROM) that_contains the_EXOS_operating system_and_a screen editor_/ word processor._The BASIC programming language_was supplied on_a_16 KB ROM module.

Two application-specific integrated circuit (ASIC) chips take some of the workload_off_of the_central_processor._They are named "Nick" and_"Dave" after their designers, Nick_Toop, who_had previously worked on the Acorn Atom, and_Dave_Woodfield. "Nick" manages_graphics, while "Dave" handles sound and memory paging (bank_switching).

A bank switching scheme allows the_memory to be_expanded_to_a maximum of 4_megabytes (4,194,304 bytes). The highest 2_address lines from the Z80 are_used to select one of the four_8-bit Page Registers in the Dave_chip. The output from the_selected register_is used as the highest_8 bits of_the 22-bit_address bus, while_the lowest 14 bits come directly_from the Z80_address bus. Effectively, the 64 KB_address_space of the_Z80_processor_is divided_into four 16k_sections._Any 16k_page_from the 4 MB address space_can_be mapped to any of these sections._The lowest two pages_(pages_0 and 1) of_the 4 MB address space_contain system ROM. The next four_pages (2_to 5)_are reserved for a ROM cartridge (max 64 KB). The top_four pages (pages 252 to 255,_totaling 64 KB) are_used as_video_RAM, but can_be_used for_storage of program code and data as_well. On_the 128k model, the additional 64_KB of ram is_mapped_on pages 248 to 251. The_remaining memory space can be used_by external devices and memory_modules_connected_to the expansion bus.

Keyboard and_case 

The case is unusual in_that it contains_both a full-sized keyboard with programmable function_keys,_and a joystick. Its distinctive shape_was_due to the designers' desire to_break_away_from customary designs. The low-profile_keyboard is constructed with mechanical keycaps_on top of a rubber membrane and has a_standard layout, but_the feel of the keys_was_disliked_by many, or even most people, because the keys weren't_"full travel",_but had a_squishy feel, similar to a Sinclair QL or Spectrum+. The_joystick replaces the normal cursor keys, and_allows the cursor to be moved diagonally. Royal College of Art_graduates Geoff Hollington and Nick Oakley