SPACE Newsletter - January 1986

January 1986

.:;r ANT_1AF1Y, 1986 T h i s mo:n.th's meeti:n.g: FRIDAY, JANUARY 1 0 A t t h e Faico:n. H e i g h t s Comm~nity c e n t e ~

Ne~t

rno:n.th:

FRIDAY,

FEBRUARY

Bruce Baug ... President 774-6226 Bob Jim Schulz . . . Vice-Pres 537-5442 Bob Frank Saug ... Disk Lib. 774-6226 Bob Jim Siede . . .. Paper/Educational

Rhode ... . Editor 222-3593 Siede .... Treasurer 489-3982 Floyd .. .. Secretary 487 - 2627 Librarian 489-3982

..=_~d::·=·=·=4=1=3=-=2=8!9:::1=================.::--, In this issue: SPACE/TAIG Bulletin B~o~ar 5 Hardware Modifications from MACC and SLCC Onderlining with ATARIWRITER and the 1027 printer Lesson 07 of Chris Craw£ord's assembly language course Plus all the usual columns

Published by the St . Paul Atari Computer Enthusiasts (SPACE), an independent organization with no business affiliation with Atari

Incorporated .

Permission

granted to any similar organization with which SPACE exchanges newsletters to reprint material in this newsletter . We do, however, ask that credit be to the authors and to SPACE. Opinions expressed are those of the article authors and do not necessarily .r eflect the views of SPACE, club officers , members, or Atari Inc.

e tt a HCmE ClJIJf\JT8i SJ?PLlES t6Sl' E. HOYT AVE. ST. PA1A.. :$!5108

<612l-n'4-622B

5 1/4 SSDD FLOFPYS 10 FOR $7.90

:3 1/2 SSDD FLOPPYS 10 FOR S20.00

BUTTONS S.50 EA 100 TO CHOOSE FROM

::~tl itff•li

~~~~

BYTES FRON THE PRES. W1il, has •Y phone started to rinq! l have had calls fro• the Twin City uea, Ohio, and Brainerd. I a1 glad to help out, av.ii if you are a 1uber - stop and say hi at the aeeting - over tht phone, evtn if ! don't always get the r1glrt na11 with the right face. Now ont of tht problen: I have recirinttd in the nnlett er articles fro■ the SI.CC Journal !S111 Leandro, CA) and the Nanitoba Atari Co1puttr Club (Ninnipeg, ltanitobal. But l can not find a copy of the 48K or 641( qaary upgrada for the Atari 400 - ont of our 111i11rs w.nts it and l would like one for our files. lf you ·havt one, pleas• call 11 at TTJ-022& 1 and l can 1akt sure III gtt 2 copiH to the 1eeting Jan 10th. I ha~e not found a 1teting place for a ~20 ST gro1q1. Would everyone :nteresttd please sign up at the 1eet1ng. Then llj@ will know how large of a roo1 to arrange for. Any questions, call 11 - uetfng nites becoN tao short to talk with each of you. Also, if l don't writa it dOIIC'I I 1ay forget it. Bring your questions in writtlffl for• and I will try tc get you the answar as soon as I can. BRUCE ltAUS, PRES. !lfftinq ~ by Bob Floyd

~tcllOt r

The last SPACE eHtin~ ~a! held F~iday, DKtlher l-3 w1th Bruc1 Haug, th1 nn pr111dant, prn1dinq. Th1r1 _,.e

7b people (10 n111l 1n 1ttendance.

Rav Douglas, fro1 the Co1puter Broadcasting ColpillV :~BCl, 11as the featured guest. Ray ·s sha•, Coaputerline Padi:: Shaw, u an IHHC-Aft 1280 radio nery Swiday fro• 10:00 - 11:00 a■, The show features ATARI ca10uters on the •irst Sunday of each eonth (ltt 's call in and s1q1port our co1puter en 37t-2o081. Ray had a d110 of the 'shuttl1 c~1aun1cator• MIiich i~ ustd to decode !likt a tcdN) cosputer progra■s or infor■ation broadcast over the radio and stored on a tap, recordar. Th1 shuttle co1a&111icator is r.ct ,et 1va1lable for Atari caaputars. CBC also oaarates a 235 on 129-1)408 - password is: CBC? Ji1 Schul:, the new vice pres10ent, reported an ST news. Ji• said that the RO"'s ~ 20 aeq hird disks art due 1n janu1ry , Star Ruders ~ IUss1le Canand due perh~s i!Ven sooner and that VIP ProfHsional and !>eqas ue htre now. J~a also reaorted the ruaors of a 3.~• disk dr1~e for the !E and that the lEll chip 1av be released. Phyllis and :arov, :ro1 Wi:ard's llcrk, reciorted that the Learning Phone (Plato cartridge! and the AiARl 300 baud aodeu would be in ~ate: I can verify that the 1odees are in. -ed. ~nnr liaug, ,ji sk ! ibnru n ~ cue c a 'ltI lt tv for •~1cro1llustrator• p:ctures fr01 the di!K of the 10nth. • &00 Siede, the new treisurer, ~eported a balance of t

$1049, • jae Dante rl!l)orted that the BBS :shaving trouble with 'BBS Construction Set• ind that it is currently unuseable:--• A SPACE ST 1inigroup 15 being fortell - ul tn1t IS needed is a 1tttting place. f The ribbon re•1nker was ardtred, out has not vet arrived, • A 1otion us 1ad1 and passea to aake the BBS sysop a ciub officer with frtt 1eabership priv1ledge£. In duos, Sardy froa Ni:ard'; Wort, reaartea on the ntw release of Atariwr?t'er Plus. [t has sany new feature s. is disk based and retails for S49.95, Bob Floyo deao d Graphics Shop. i Print Shop ~tility tc convert "Kicroillustrator• ~r •Paint• screens to Print Shop pictures, It was not dnything too great, but still useful. Todd Burkey, of Ninatools, de10 ·,3 Sil!!nt ~ ' a subun ne gue. O.D.11. ~ews

By:Frank Haug Happy ~e• Year\' ~ell, tnis 1onth's aisK 1s a little skiapy, I 111st ad11t. This 10nth i was once again UNDERwttel1ed by tha donations. ~~, ?eople: You 1ust have SOI£ prograas you COULD donate. Nuff said. I'd lite to use this space to explain new to oroer put disks. tf I don't have the disk you' re iooK1ng for at the 1Nting , you should ?RINT your nan, the.disks you •tnt, and (cptiooall your ;hone t, Ocasionatl"Y I run into problees •ith the ~rders !For ex.aole, poor handwriting or an order for a non-existing disk. l. ln such instillces i would call you ta clarify 1t. This aonth •• •ill be seli1ng s double-sided picture disk for So, Si1ph boot the front side ~, BASIC 111 "-rder ta •,iew the pictures. To View tne Hip side, hit aREAK 11hen a picture is beinq displayed, ilic the aisk ind type

C~••

RUN.

No• on with the progran on this tonth ' s disk. 1.DIMOND - A clone ".f the 1rcade ga1e 'The Pit ' , 'four ship is low on fuel. Sather tne cia■onds before 1t blo11s UP, :.PHARTONB.3AS -(ou ~st get :ne kevs to !!Scape the tcab. To see further 1nstruct.ons run oroq.13 3.TONBINST.aAS - !nstructions for t2. •.PEB:ASSN.BAS -This progra ~11! put the values of user d1fin1d ae■orv locations into a di~i string ~ disk

file.

Hooefull,,, I 11ill h.we aadcd 110:-e prograas before tile ttetinq. This 11ebng I <1ill (! h00e1 ,ave ..t !east tllO c001es ~f each JON we sell.

SPACE JANUARY, 1985 PAGE 2

·oe ~

,,.. ~CHRIS CRAWFORD

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ASSEMBLY LAH&UAGE COURSE EXCLUSIVELY FOR USE ~F ilORLOWIDE USERS NETWORK LESSON SEVEN: INTERRUPTS

now approach one of the 1ost difficult topics in the ijorid of asse1aiy: interrupts. This is such a nssy topic that very few hign-level languages uke any provision for interrupts. Moreover, interrupts are ane of the but ways around crasn your progra1 hard. Prograaurs using interrupts ,ust be very careful. ~

The standard way to handle this prollle1 is with a techn1Que called polling. Your progra1 runs out every n011 and then ta check ieftether the hig'h-priarity situation has arisen. If it has, then the progra1 responds to it. If not, it returns to its original 110rk. The proble1 with polling arises fro• the choice of polling interval. lf you choose a long linfrequ111tl polling interval, then you •av not respond ta a de1and quickly gnough. If you choose a short !frequent> polling interval, then vau will respond quietly to the deund, but you will ~ever nave il!Y ti1e for your regular coaputations. Yau HY think tliis type of situation is infrequ111t, but :an list quite a few situations lliere this is fairly coHon. l'lost UC operations involve short burrts of ~~•outation at infrequent intervals, but they 1ust be attended to an a tight schedule. For exaaple, talking to a cas:!t:e 1ect involves very little real work frot the CPU. t:ut 1t 1ust be done according to a precise scheilule. E·ien a Uisk drive is ·,ery s1011 bv the standards of a 6502. Cr how about keyboard response? When the huun operator presses a button, he ttil\ts ta see response NON, not two or three secanas fr01 na.. Yet he coulo press that outton 1t any tiae. Sa should your progra1 sit on its nands ~.iting for i keypress, or should it ignore the huaan operat:::r" The solution to all of these probleas is the interrupt. Hn 1nt2rruat 1s rather like a subroutine that can be calleil b a hardware action. There's a ttire going into the &502 called !RQ (Interrupt Request). That wire is norullv ,u1et. eut tthen sonthing iaportant happens, like a kev::ress, the :01puter's hardware puts a signal on that •ire t~ 1~terruot the 0502. Here's what haooens next: running a pragraa, but lfflen it gets the !irst checi:s the 1-oit llnterrupti in :~e orocessor status r2g1ster. if tne l~it is set, 1t jeciaes t:: ,gnore the interrupt, If it 1s clear, it

71e J502 is busv in~=rr•Jpt signal it

~roceeds to the next steii. !t saves the orocessor status register and the current 'lalue of the prcgraa counter :into the stack. Then it loads the progra1 counter with the address stared at a special 0lace in RD" -- it's either $FFFC or $FFFE, I can never qet it straight. !t thus ju1ps to the address specified tn RON. It expects to find an interruct service routine there, llhich presu1ablv will deal with the keypress in the apprapriate .tanner. This routine will ?rOballlv start by pushing A, l. anti 1 into the itack to preserve the•. When done, the rout:ne will then pull the1 aff the :tatk and execute an RTI instruction, which causes the b502 ta pull the processor status register otf the stack, and then pull the 0rogra1 counter aff and resu•e operating. The isportant thing ibout this rather cotl!llex sequence

is that it alloM the b502 to drop llhatever it is doing,

servite the interrupt, illd then return to its earlier functioning without skipping a beat. The overriding goal Jf all this is to be absoiuteiv certain that, when the c502 reeturns fr01 the interrupt, it returns in EXACTLY the same state that it ttas in when the interrupt hit. Otherwise, ill sorts of horrible, untraceabl.e bugs would result. laagint - you're in the aiddle of so1e huge coaputation when an interr1Jl)t strikes. It subtiv changes s011 'ltrY tiny para1eter, just enough to insure that lffltn the

coaputation resu1es, it will be slightly incorrect. When you try to find the bug, you discover that s01eti1es the code works perfect! v and soaetimes it fouls up, ana you can't figure out lffly it should do that. Very bad business:

~oral: interrupts aust follow a very tight disciciine if they are to be of anv ut1l~ty. Mow let· s get into soae of the technical gore invoi nng interrupts. First, there are two interrupts an the 0502. Thev are callee [RQ \lnterr·Jpt Re<1uestl ana NIH (Nan-llaskable [nterrupt:. ~he idea is that the !RQ canoe 1asked out bv setting the l-b1t ~ith the SEI 1nstructicn. Then '!OU use tne CLI in:truction ta clear the l-!lit. Thu5, IRD is useil far interrupts that have secoM ~riorit-,. NIU is resened for first-pn oritv lnterru;its. It is not aaskaole. Ho11ever, the designers .Jf the ~t.n ::0111uters routed !RQ and nMI tr.rough the PDKEY and ~:me Chil)S

rescacti ·,ei'{. ~nd they ilut 11asii: registers into these :hioi;. Thus, the run :ar. oe :nasxeti out after ail -- out Jnl i an Atari ::01puters. Jther :i502-lJased co10uters acn · t allcw t!lat.

SPACE JANUARY, 1985 PAGE 3 I

The·NNI and IRQ interrupts have separate interrupt vectors in ROft, sa they can be treated differently. These vectors route the interrupts ta the OS, but the OS is surt enough ta route interrupt fla• tharuqh so11 RAIi locations. This uans that you can interce,t thne ho interru11ts by altering the contents af the RAN-vectors. II llGl'l't list thn here, there an a nulbtr of thN for different · si tuatians. l

can freely. 11rite to ·1ariables used by the •~inline, you A will certainly have proble1s when the sa1nl1ne atte■ots tc;a, work •ith variables whose values change in unpredictaole Miys. You 111st set ~p ironclad rules about !lien the ISR can aess •ith variables used by the 1ainline, .nat it can do ta the1, and hDN it notifies the ■ainli~e routines that it has indttd altered the1.

Yau 111st be careful, thougll, lli111 altering such a RAN vector. llhat happens if an interrupt strikes after you have changed one byte of the address and before you have changed the other byte? The 6502 •ill fly off into never-never 1and and you have trashed. Sure, it •s unlikely, but qaad proqra...,.s don't c0W1t an luck ta 11kt their pragrus 1tOrk. You have ta guaranta tllat tlle interrupt ltOR't occur btfare you uss •ith the vector. Use SETVBV fra1 the OS.

pa•erful, but every

The tMO pri1ary applications af interrupts with tht Atari ca141uters are for VBis !Vertical Blank lnternqats) and DLis !Display List Interuptsl. Thut art VlifY involved topics covered quite tharauqnly in the booi Dt Rt Atui, YBis are 10st often ustd for aniutian ca■tral, input handling, and other ti1.-critical operations. Far uaepla, the entire player I/0 of ry gaa £.stern Front 11941) is handled by VBis. Tht scrolling, giving of ardtrs, identifying units, and so forth is all dont by Vlls. The 1ainlin1 rautint Hanllllile figures tht wtificial intelligence. Dlls are ustd ta enhance the graphics an the scrttn. You can get aore colors, aare use out of players, aare scrolling, and aore character sets with proper 1111 of DLis. Again, consult De Re Atari for a full treat1tnt of this coaplex subject. Interrupts are estreMly difficult ta debug bteause thty tend ta crash the syste■ llhen they fail. Yau eust exercise the strictest discipline in .riting interrupt code. Ti1ing prable■s, seld01 of concern in uinlint prograaing, can beco1e critical with interrupts. Whit happens, for exu,le, if your interrupt service routine takes so 111ch execution tin that ■are interrupts arrive thill you can service? Bad things, I issure you. You 11tst always ask younelf, Mhat ha11pens if an interrupt strikes here? Or thtre? Vau 11Ust asslllt that an interruat will strike it the 110rst possible ti ■e, and .rite your code ta deal with that possibility. The aost i1p0rtant discipline ta folio• in writing interrupt service routines is this: keep your interrupt database separate fro1 your aainline database. If the ISR

Approach interrupts •ith extreu caution. They are very pragra■aer can tell you horror stories about debugging interru11t routines.

Atari 1027 Printer, AtariWriter a::d underlining InfoWorld say~ the Atari 1027 let~er Quality printer "does have one of the finest underli:.es we have :.v _r s,Ln o~: a ho:::e-compute:- printer·. " Unfortunate ly the combinatio~: ~f AtariWriter and the 1027 is neither covered in the AtariWr:. ter manu.;;;.l nor , -the printer book. And $20 for a pri.~ter driver seemed high for the underlir.i~g capability. 'Ibis article will tell you how at the cost of a few mo~ents ci y:ur time.

I£

YOU have the 1982 version cf

AtariWriter , read on. I£ you have the V 1984 version, the 1027 is one :f the printer optior.s and you should::·t need this article. To begin ur.derli:ii~:g , put ':he c-:..u-so:under the first =h.::racter you wish to underline. 'Iben '.1old t!1e contr:.l key "'-'-ter th.: key for ·-h while taoing down - -~ l _..., . "o " once. case lcwer the iz 'Ibis (Ncte: 11 11 and no~.... th e c~pital " O" as me~tioned 0 in the ANTIC article b~low.) This "O" on tha scr~en should put an inv.:;rse ~h .... (a dark letter "0 11 ins -4 de a ·..,.,..~ -· -s- ~ rectangle). ?ell ow ~h;; inv.erse "O" wi· ....... th e number II 15. II Tae char~~ters you ~•• wish underlined sh:uld follow immediately without and spaces. !=.mediately af~ar the l~st chaz-acter you want underli::ed, hold tha control key down and t:,'J)a ar:oth1a:r in·,:erse "O." -u::iber t::,:,e 'Iben without a s-o::-.ce ............ ..- -'-h-=. "14."

More infor:iaticn ::: At~:.Wr:. ter ,,,..d printers may be four:d in t!.e March 1985 ~ . pages 34-36. 3y ':he_wa~, a $2 bot~le of Stamp Pad Inker Iluid ::-om Tar~et ca.: rei:-.k the ink roller on the 1027. The above is:. sample of the type and underli::.:..-:i of the 1J27

SPACE JANUARY, 1985 PAGE 4

Larry Vande~ Pl~s

··.__/

SPACE JANUARY, 1985 PAGE 5

•

ANALOS D,0.11, Bob Floyd I 11ill have the Dece1ber 1 1985 1137) and January, 198b (138! Analog Coaputinq disks for sale at the ueting, Price is $4.00 each for registered Analog subscribers only. i 11ill be enforcing this rule no11 11ith !!J!. exceptions. Here· is a list of persons who need to (re-lregister their You 1ust bring a current issue subscriptions 11ith u. label: wiling sho11ing your nan on the Bob Arl:o Paher Iverson Kris Kruger Anna Shavers

Jesse Fleury Robert Pech ■an Donald Overland Tony Walsh

UPGRADE SYNCALC FOR 1:30XE OWNERS SEND Sl0.00 & DISK

BRODERBUND 17 PAUL DR. SAN RAFAEL, CA. 84903-2101

810 Write Protection by Choice . Circuit By Andrew Sametz Article By David Reid (See Figure 4 on different page)

BEAT THE CROWDS

pretty be can disks Notching it void your painful. Not only does but you could warranty on the disk, This destroy the disk by doing it. little wiring trick to your 810 drive will allow you to write on a disk, ignoring a write protect tab or a nonIt will also allow you existent notch. Of to not write on a disk at all. course you can let the drive operate normally.

WIZARD'S WORK

JANUARY CLEARANCE ----------------------------SALE 8.18

WRJ:T.E PROTECT ION BY CHO:ICE RED

Parts List OPDT center off toggle switch Red I.ed wire is easy to build, and The circuit can be made within an hour. The toggle switch and Led can be mounted where If you.don't want to ever you want. you d~ill a hole in your drive. case, can tape or glue th~ ~witch to the (1ns~de). To move bottom of the drive open the drive door, and the switch, reach in and move it. This is a good circuit ~o bui~d.and it's not very hard, Happy Disk Writing.

BLACK figure 4

LED L E D

RED

DPDT TOGGLE SW:ITCH.,CENTER OFF.

""ba••-••• Hard•••• By Jay Torres

switch Hardware ResetReid

By David (See Figure 5 on differen t page}

Did you now that you can damage your computer by turning it on and off? Well for the 800/400 this applies only compute rs. The reason is simple. Every the time you turn your computer on. power from the power supply hits the regulato rs and sends a surge of power through your computer . This will slowly and eventual ly damage your computer . The new computer s could kill it. correct this problem by having the regulato rs in the power supply. That every time you turn on your way. computer . there won't be a power surge. So how

can you

prevent this?

The

But easy way is to use system reset. or a sometime s your computer hangs. program will

not reboot

when you

hit

system reset. The other way is to use a The 6502 CPU will hardware reset.

reset it self· if told to. By groundin g pin 40, it will be told this. When you press the switch the CPU will reset, and simulate s turning the power off and on. I have modified my Atari 800 with Hopefull y it will last a the switch. few years longer.

HARDWARE RESE T SW~TCH MOMENTARY BUTTON SWITCH

PXN ~

GND

6 5 0 2

C p

figu re 5

By David Reid and Andrew Sametz

In this article I propose to show you how to modify an Atari 800 to I will also provide 96K of usable RAM. show how to boost memory higher to include a 160K and 288K Disk Ram full allowing version Capabil ities. 16K Memory Board Modifica tions Remove the center 16K memory board (or use a spare) and install the 64K modifica tion. Look at the RAM board. The eight chips along the top are the RAM chips.Th e other four are addressi ng chips.

You shall need to remove the 12V and -5v sources on the board and move the 5V source to where the 12V used to be. As shown in Figure 1A. cut the trace boards"s edge of the X from pin Also cut the trace connecto r to C521. going from edge pin Y to C523. Make the cuts cleanly and be careful not to damage adjacent traces.

The trace and CS23. Remove C521 using a coming from pin w carries 5V. short piece of wire make a solder bridge between this trace and the old 12V trace at the point where CS23 used to be. Next. remove C503, CSOS, C507, C509, cs11. CS13. C515, and C517. Remove the eight 16K RAM chips and in their place. insert the 64K RAMS

SPST

using an ohmmeter insure that there is no connecti on between edge pin Y and pin 8 of the RAMS. There should also be no connecti on between any two of the edge pins w. X, and Y.

Assuming all has gone well the board 16K should function exactly like a board since we have not changed the addressi ng circuitr y. Now is a good Put the time to check the board. modified board in the center memory slot of the 800 and check to see that it function s normally as a 16K board. then recheck all of your If not, work •••

PXN

•

(Reprint ed from Windhove r Project) Correcti ons and article modifica tioffs

RESE T

Now remove the 5V supply from pin 9 of the RAMS. To do this. cut the wide trace on the chip side of the board as shown in Figure 2A. Get a 74LS158 chip and use a pair of carefull y bend up needle nose pliers, a. 15, all of the pins except pins 1, Remove the chip at ZS03 from and 16. it's socket and place the 74LS158 on the top so that the four pins not bent touch the same four pins on the lower Carefull y solder the four pairs chip. together . Next. solder a four inch piece of wire to each of the pins 2, 3, and 4 of the top chip. Set the chip pair aside

SPACE JANUARY, 1985 PAGE 6

'-...,,I

V..ni,oba

•

October 85

A<ari Compueec Club

at this point . we will prepare the three Next, additior. al ICs for mounting . These will so be mounted in the "dead bug" style, it may be a good idea to put a stick-on label on the undersid e of each IC to indicate its type and the location of pin 1. Install the new ICs in the vacant I used small below the RAMS. pieces of double sided tape in case I A drop of would need to remove them. super glue will work but be sure to do it right the first time. space

Now wire the chips accordin g to install the chip pair figure 1. Next, set aside previous ly into Z503 and complete it's connecti ons. At this point connect a jumper between pins V and w.

temporar y

the Replace the memory board in center memory slot for testing as a 16K board. If the blue screen does not come turn the computer off up quickly, IHH£I>IATELY and recheck your work. If the board checks out all right, remove the board from the computer and remove the jumper between V and w. Now cut the circuit traces connecti ng pins H to N, P to R, and S to T. The 64K board is complete . aside for now.

Put it

Remove the two remainin g 16K boards from the computer . On the reverse side traces the find board each of and S P to R, connecti ng pins M to N, to T. Cut these traces on each board. Reinstal l them in the compute r's first and third slots.

Persona lity Board Modifica tion Remove the ROM board and take it out of it's case. Connect a jumper between Z401 pin 7 to edge card pin 20. Do not allow solder to run down the card edge pin. Reinstal l the ROM board in the computer . Motherbo ard Jumper Installa tion It is now necessar y to modify the Disassem ble the 800 800 motherbo ard. and place the motherbo ard upside down with the joystick ports facing away Using figure 5 as a guide, from you. fine install seven jumpers using a solid conducto r, insulate d wire. paying Carefull y check your work, particul ar attentio n to correct pins, solder bridges and shorts. Reassemb le the 800. The modifica tion

is complete .

P'inal Testing computer the assembli ng After reinstal l all of the cards with the 64K Power board in the center memory slot.

up the computer and wait for the blue screen to appear. As before, if it does not come up at once turn off the computer and recheck your work. then normal is all If You now have an Atari congratu lations! 800 with 48K of normal memory and 48K of extended memory. When used with Windhove r DOS 96 this provides a 360 sector, single density, virtual disk. 128K Ram Board Option The 64K modifica tion may be extended of more by the addition to 128K decoding chips and 8 addition al 4164 RAM chips. The second set of 64K chips are placed piggy-ba ck on the first set with only pins 15 (CAS2) elevated and bussed together . Cut the CAS trace near Z502 as shown in figure 2. Mount the 74LS157 all pins Z504 with piggy-ba ck on and 16. 15, elevated except pins 8, Wire the elevated pins as shown in figure 3. When used with the Windhove r DOS 160 this option provides a 720 sector, single density virtual disk. 256K Ram Board Modifica tion is now The 256K x 1 RAM IC (41256) availabl e. When the price is right, you can use them by simply installin g five 64K to the addition al connecti ons enhance -nts. Make the substitu tions as shown in Figure 4 and substitu te the 256K chips. This ·option provides a full 720 sectors of single or double density virtual disk with RAM left over to use as scratch pad, multiple display lists, etc. The possibi lities for the use of this extra memory are almost endless. Use of the RamDisk when running AMODEM will signific antly reduce both upload and download time along with your phone Disk duping becomes extremel y bill. easy when you use COPY•.• to copy to Programs and from the virtual disk. which leave your drive spinning fo: extended periods of time can often be modified to perform faster with no wear on the drive. The Windhove r Project has develope d a DOS which will access the extra memory and make it work as a virtual It is 100% compatib le with Atari disk. It allows rebootin g from DOS 2.0. RamDisk followin g system reset, allows an instantan eous call to the DUP.SYS, generate s a HEM.SAV file to save data you were working on in memory and is availabl e from me in versions for use with the Atari 400 with the 64K RAM modifica tion as well as the Atari 800 RAM 288K and 160K, 96K, with modifica tions. Price on the Windhove r DOS is S20 includin g the disk and documen tation (S15 plus $1.50 postage and handling . If you opt if you send a disk to me.)

SPACE JANUARY, 1985 PAGE 7

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SPACE JANUARY, 1985 PAGE 8 CPU

Hardware Mod CLAUS BUCI-HOLZ A

t30XE-CO,-PATIBLE 256K UPGRADE FOR THE ATARI SOOXL

I designed the 2561< upgrade described In my artlcle, "The Quarter-Meg AtarJ" CBYTE, Septeamer-, 1985), In Decanber-, 1984. Since this predated the 130XE, there was no precedent for extended manory on the XL' .s. I felt free to Implement a system of eight 32K banks. The major reason was to keep the add-on circuit as simple as possible. The 130XE, Introduced In ear Iy 1985, set a different standard for bank-select memory. It uses 16K banks and makes them separately aval lab le to both the CPU and the video control Ier (ANTIC). The XE has 128K tote I M110ry. The 64K extended RN4 Is sp I I1' Into four 16K banks. A 2561< 800XL has 192K extended RN4, which requires 12 16K banks. I have designed a new upgrade for the 800XL that Implements such a sch.... Its similarity to the 130XE 's scheme a 11 ows use of software for the XE on a 256K 800XL. To select one of four banks, the XE uses two bits, 12 and 13, In the manory control register (port B of the 6520 PIA, addressed at SD301 or 54017 dechnal >. Zeroing bit 14 Nkes the selected bank appear at addresses ~OO-S7FFF C16384 to 32767 daclmal>, as seen-by the CPU. Zeroing bit 15 makes It appear there as seen by ANTIC. In ray upgrade, bl-ts 12, 13, 15 and 16 se Iact one of the twe Ive banks. Zero Ing b It 14 makes the se Iec:ted bank appear · at S4000-S7FFF to both the CPU and ANTIC. So, any pr-ognm for the XE that uses the extended RN4 for CPU storage w111 work on an 800XL with this 1110d. Those programs won 11' use the addl1'fonel 12SK, though. Progra11S that use the vlda, banking feature of tfie XE might run on the 110dlfled XL, but the screen di sp I ay wl 11 be wrcng. . The procedure for this upgrade Is baslcal ly the s - as In the ar1'1cle, except for the followfng points. If your. ANTIC (U7) par-t nllllber Js C021697, use the clrcu It • of the figure, axclucUng the area I nslde the· dotted I Ines. If 11' Is 'ttle C012296, Include the c Ircu I1' Ins I de the dotted 11 nes. The. circuit requires five connections to the Ptk CU23). So pins 12 111rougfl 16 IIUSt be bent· up and ccnnec1'8d to -the c Ircu It. The rest of the procedure Is the saae. Notfce 1'ha1'. this clrcul1' ha ON ll0f"9 clalp than TN: artlcle'• clrcuf1'. Thia Is TN price of. CCllpatlbl 111-,.

back on • Otherw Ise It may not· co Idstart properly. Mv orlQlnal RN4dl..&k .oftware doesn't work with this new mod. Enclosed Is a llstlng of the new version. It Is used I~ the same way, except that It offers a choice of either two single-density RAM disks or one double-density. If you wish a disk copy of the source and object code, send me a blank disk and return mallerwith full postage, and I wf 11 pranptly · send ft back with the software (Claus Buchholz, 20tC East Edgewood, Lans Ing, _Ml 489 t O>• Al-tern ate Iy, you may download the software from the Capitol Hf 11 Atari Owners' Society 88S at 517-37t-t106 or from the Castle Co•unlcatlons board at 517-371-4234. The source flle Is called ~GXLO.SRC for Quarter-MEG XL Double. AI so ave I Iab Ie Is a RAMd Isk program that sets up one single-density RN4dlsk and leaves the XE-equivalent banks free for XE software. This Is quite useful with BASIC XE, DOS 2.5, or the new Synapse software. Its name Is (14EGXLS.SRC. I ask one thing In return for this Infonnat Ion: p Iease pass It around to a I I your Interested friends. Put It In your club's I lbrary or on your favorite BBS. Encourag Ing software support of 2561< wI 11 result In many Interesting uses for It. Thank you and enjoy! P.S. In response to an often asked question, I state that I have no documentation for my 192K upgrade for the 800. It Involves modifying an Axion 32K board to Imitate a 128K Axion RNC)ISK and upgrad Ing an Atar I 16K board to 64K. It Is a dlfflcult mod, and I rec01mend the XL 1110d Instead. · CSLCC JO~AL EDITOR'S NOTES: We reco-.nd reading the BYTE artlc:le Nntloned above for a better description of the basic a>dlffcatlon, then apply this article's lnfonaatlon to your IIOd.) PARTS LIST 8 41256 256K-blt dyn•lc R#I (200ns or .Jess) t 74l.S153 Dual -i-to-1 a111'1plaxer

1 741.S139 Dual 2-to-1 decoder 1 33 ohll, 1/4 watt resistor I Rad 1o Shack I 276-150 c Ircu It board 1. U5-p In DIP header and short r I bbon cab I• 3 16-pln low proft le sock.ta ADDITIONAL PARTS FOR ANTIC IC012296

Wf'ttl tbe 2'8 dynalc RMs In your XL,, 1 74LS393 Duel -i-bl1' counter to wal1' ff leut tN seconds af1'er 1 16-pln low prof I le soc:k.t turn Ing TN COllpUiw" off betcre voa turn 11' . 1 14 In I ow rof 11 e -,cut

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SPACE JANUARY, 1985 PAGE 9

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256K FOR 800 XL, ATARI 130 XE COMPATIBLE - by Claude Buchholz , SLCC

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SPACE JANUARY, 1985 PAGE 10

Using an IBM Monitor

Low Cost

Parts List RGB

(Schematic Reprinted from Bay Area Atari User Group. May 1985) Article modified by MACC (See diagram on a different page)

if you This is a useful circuit happen to have an RGB monitor and an old Atari 800 computer. Before now, you could never use a RGB monitor with your Atari. This circuit will allow you to do this. The circuit given is for use with an I do not know IBM compatibl e monitor. if it will work with any RGB monitor. I will tell you how to modify the circuit so that you can use any other monitor. Common Procedure s For those with RGB adjustmen cs on is the installati on their monitor simple. The soldering of the five wires to the appropria te pins of the A103 chip and the soldering of the five leads to a chassis mounted 5 pin female RCA plug finishes the job (Fig. 1). For all other owners of just simple RGB video input with no separate RGB controls you just follow the schematic (Fig. 2) and make the same soldering connection s as in the first example. We find it is easier to use a 14 or 16 pin DIP socket to solder all four transisotr s on with the 68 ohm and the 500 ohm (sic) potentiom eters. This way yo~ ~an do a clean insta~lati on by drilling three small holes in the side of the chassis for mounting the three potenti0111 eters with a good two part epoxy so you can have easy adjustmen ts a small RGB output with of your screwdriv er. Then at the same time you can epoxy the 14 or 16 pin DIP socket to the inside of the 800 cabinet.

Bob's Blurb A note fro ■ the editor

First of all, let 1e express •v appreciation to the 1e1bers of SPACE, all of Kho■ sho11ed concern for 1y printer proble1s. I Kish [ could have coae to the ■eeting t~ soak 1JP the svapathy in person! What happened Mas this: Kysteriously, overnight, av APE-FACE printer interface died. [t had Korkea prefectly since the day [ bought it, and I had been using it the night before. But, 11ouldn't you kno11 it, on the night I "as ?Utting together the final copy of ay first ne11sletter to be printed the next ~ay, it didn't •ark at all. All of ~• software said "printer offline• or "device unavailable.• '3i nc:e the printer aid 1 t · s test pattern okay, that aeant ·· :~at the interface Mas a.t fault. I ~ent 1n to Wizard Works a. couple days later and the lovely !adv gave :ae a r~lace1ent. once again, [ appreciate your concern. Next on the agenda, someone left a hat at the last ~eeting. [f anyone is 11ssing a 1an·s hat, the officers :h ink 1t would be swell If you reel aued it.

3 - 2N2222 transisto rs 1 - 2N2907 transistor 4 - 68 ohm resistors 3 - 1 Kohm resistors 270 ohm resistor 1 1 - 470 ohm resistor 3 - 500 ohm potent~om eters 1 - 1 Kohm potentiom eter 1 - 14 or 16 pin DIP socket 1 - RCA 5 pin chassis mount female plug Some wire Using an Other RGB Monitors Parts List 4 - 2N2222 transistor s 4 - 68 ohm resistors 3 - 500 ohm potentiom eters 1 - 14 or 16 pin DIP socket 1 - RCA 5 pin chassis mount female plug - Some wire The changes on the circuit (Figure 2) are minor and should be done before you start making the circuit. ohm 1K all eliminate First, resistors (Do not connect the 68 ohm Next resistor to the 500 ohm pot!). eliminate the 470 ohm resistor but this time connect the transisto r to the 2N2907 The transisto rs. other changed to a transistor should be 2N2222 (connect the emiter to the 68 Now remove the 270 ohm ohm resistor) . Do not resistor and the 1K ohm pot. And finally connect connect the ends! the base of the new transisto r to_Sync In. you can If you have any problems, check the newslette rs in the newslette r library (HACE June 85, ACE April 85).

The third thing I have ta say is that the articles in this 1onth's ne11sletter fro ■ MACC ("anitoba Atari Ca1puter Club, Ontario) and· SLCC (San Leandro Computer Club, San Leandro, CAI involve soae pretty sophisticated work inside your co1puter, and unless vou feel quite confident of your soldering skills, vou should probablv not try these · ;1odifications on vour 0110. ·

SPACE JANUARY. 1985 PAGE 11

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