тHE MATERIAL CONTAINED IN THIS DOCUMENT IS OF AN EXPERIMENTAL NATURE. аS SUCH, ALL CONSEQUENCES RESULTING FROM THE USE OF THE INFORMATION IS THE EXPRESS RESPONSIBILITY OF THE USER. тHE AUTHOR SHALL NOT BE HELD LIABLE, AND IMPLIES NO WARRANTIES OR GUARANTEES WHAT SO EVER. тHE AUTHOR DOES CERTIFY THAT THE INFORMATION PRESENTED WAS CORRECT, TO HIS KNOWLEDGE, AT THE TIME OF THE FIRST DISTRIBUTION OF THE DOCUMENT. тHIS DOCUMENT AND THE INFORMATION IT CONTAINS IS THE SOLE PROPERTY OF THE AUTHOR, WHO RETAINS ALL COPYRIGHTS, AND PATENTS TO THE MATERIAL PRESENTED. тHE AUTHOR DOES GRANT A LIMITED DISTRIBUTION RIGHT TO ALL IF THE FOLLOWING CONDITIONS ARE SATISFIED: тHE DOCUMENT IS DISTRIBUTED IN COMPLETE AND UNALTERED FORM, WITH THIS LEGAL FORM INCLUDED. нO COMMERCIAL DISTRIBUTION (IE. PUBLISHING) OF THE DOCUMENT IS ENTERED INTO WITHOUT THE WRITTEN CONSENT OF THE AUTHOR. лASTLY, NO MONIES SHALL BE EXCHANGED FOR THE DISTRIBUTION OF THE DOCUMENT, EXCEPT FOR REPRODUCTION AND SHIPPING CHARGES, WITHOUT THE WRITTEN PERMISSION OF THE AUTHOR. вITH THESE CONDITIONS FULFILLED, THE LIMITED DISTRIBUTION LICENSE GRANTS THE HOLDER OF THE DOCUMENT TO OTHERWISE FREELY DISTRIBUTE, AND STORE IT IN ANY MANNER. бEYOND 512 KB: тHE тWO мEGABYTE реу ----------------------------------- бY аNDREW е. мILESKI цOPYRIGHT оCTOBER 3, 1989. иN жOLUME 9, иSSUE 6 OF THE тRANSACTOR, пAUL бOSACKI SHOWED US A MIRACLE; THE ONE MEGABYTE ц64. пAUL HAD DEVELOPED AN ELEGANT METHOD OF ALLOWING THE ц64 TO ACCESS THIS EXTRA MEMORY OUT OF THE ц64'S OWN MEMORY MAP. уNFORTUNATELY, THIS EXTRA рам IS RATHER DIFFICULT TO ACCESS, NOT ALL OF IT IS AVAILABLE TO THE USER, AND ц128 OWNERS CANNOT EXPAND THERE MACHINES IN THE SAME MANNER. тHE CIRCUIT NECESSARY FOR THIS FEAT ALLOWS A ц64 TO USE 256 K рам CHIPS, INSTEAD OF THE 64 K рам CHIPS IT WAS DESIGNED TO USE. аLTHOUGH A BRILLIANTLY SIMPLE CIRCUIT, IT IS OVER-KILL WHEN ONE ALREADY HAS A рAM еXPANSION уNIT (реу) THAT DIRECTLY SUPPORTS 256 K рам CHIPS! еXPANDING A реу IS RELATIVELY SIMPLE, AND IF YOU ALREADY KNOW HOW TO PROGRAM A реу YOU CAN EASILY TAKE ADVANTAGE OF AN EXPANDED ONE. иN FACT, ALL YOUR SOFTWARE THAT USES A реу IS COMPLETELY COMPATIBLE! нOW ARE FELLOW ц128 OWNERS CAN EXPAND THEIR MACHINES EASILY TOO, SINCE THE EXTRA рам IS ACCESSED OUT OF A реу, AND NOT OFF A MODIFIED MOTHER-BOARD! иN A 512 KB реу, THERE ARE TWO DYNAMIC рам CHIP BANKS ON THE CIRCUIT BOARD. тHEY EACH CONSIST OF EIGHT, 1 BIT BY 256 K DYNAMIC рам CHIPS, WHICH GIVES US OUR 512 K BYTES. тHE реу'S INTERNAL BANK REGISTER AT $дф06 WORKS IN 64 KB INCREMENTS, AND HAS ONLY EIGHT OF THESE реу BANKS. бANKS 0 TO 3 ARE ACCESSED OUT OF CHIP BANK ONE (у2 TO у9), AND BANKS 4 TO 7 ARE ACCESSED OUT OF CHIP BANK TWO (у10 TO у17). пLEASE NOTE THE DISTINCTION BETWEEN CHIP BANKS, AND реу BANKS. нOTE: SIGNALS PRECEEDED BY AN ASTERISK INDICATE THAT THEY ARE ACTIVE LOW дYNAMIC рам бASICS ------------------ дYNAMIC рам MEMORY CHIPS ARE CONSTRUCTED WITH MULTIPLEXED ADDRESS INPUTS. тHIS MEANS THAT THEY CARRY DIFFERENT INFORMATION AT DIFFERENT TIMES. тO ACCESS A PARTICULAR MEMORY CELL, WE FIRST SUPPLY THE CHIP WITH HALF OF THE ACTUAL ADDRESS, A ROW ADDRESS. нEXT WE LATCH THIS ADDRESS INTO THE CHIP BY ASSERTING THE рOW аDDRESS сTROBE (*рас). нOW WE SUPPLY THE CHIP WITH THE OTHER HALF OF THE ADDRESS, THE COLUMN ADDRESS. оNCE AGAIN WE LATCH THIS ADDRESS INTO THE CHIP BY ASSERTING THE цOLUMN аDDRESS сTROBE (*цас). дEPENDING ON THE STATE OF THE вRITE еNABLE (*ве) SIGNAL, A READ OR WRITE MEMORY CYCLE WILL OCCUR. уNFORTUNATELY DYNAMIC рамS FORGET EVERYTHING UNLESS THEY ARE REMINDED, OR REFRESHED. тHIS MUST BE DONE ABOUT EVERY 4 MILLISECONDS! тO REFRESH THE MEMORY A рас ONLY CYCLE MUST BE DONE FOR EVERY ROW ADDRESS. тHIS MEANS THAT ONLY THE ROW ADDRESS IS LATCHED INTO THE CHIP; THE COLUMN ADDRESS IS NOT NEEDED HERE. тHE ENTIRE ROW OF DATA STORED IN THE CHIP WILL BE REFRESHED, AND OUR DATA WILL BE SAFE FOR ANOTHER FEW MILLISECONDS. иN A реу THE рам еXPANSION цONTROLLER (рец) CHIP TAKES CARE OF ALL THIS FOR US. фOOLING THE рец --------------- сINCE A реу WAS ONLY DESIGNED TO ACCESS 512 KB OF EXPANSION MEMORY, WE MUST FOOL IT IN ORDER TO ACCESS MORE. вE DO THIS BY LETTING THE реу THINK THAT IT HAS ONLY 512 KB AVAILABLE AT ANY ONE TIME. тHIS MEANS WE NEED SOME WAY TO SWITCH BETWEEN THE EXTRA BANKS OF MEMORY. тHE CIRCUIT SHOWN IN THE SCHEMATIC HELPS US TO DO THIS BY ADDING TWO BITS TO THE реу BANK SELECT REGISTER. тHIS TWO BIT OUTPUT PORT LETS US SELECT ONE OF FOUR BANKS OF 512 KB. сO IN OTHER WORDS, ARE реу NOW THINKS IT IS FOUR SEPERATE 512 KB реуS. нOW WE CAN EASILY ACCESS UP TO 2 мB OUT OF A реу! хOW THE CIRCUIT WORKS --------------------- тHE SECRET TO EXPANDING DYNAMIC MEMORY LIES IN THE *цас SIGNAL. сINCE ALL THE рам CHIPS NEED TO BE REFRESHED WITH *рас, WE DON'T DO ANYTHING TO THIS SIGNAL AND PASS IT TO ALL MEMORY CHIPS. тHIS LEAVES US WITH MANIPULATING *цас. мANIPULATION OF *цас IS THE JOB OF иц1, A DUAL TWO TO FOUR LINE DECODER/DEMULTIPLEXOR. иT IS USED TO DIRECT THE рец SIGNALS *цас0 (CHIP BANK ONE), AND *цас1 (CHIP BANK TWO), TO THE CORRECT BANK OF EIGHT рам CHIPS. вHEN ONE OF THE рец цас SIGNALS IS ASSERTED, THE цас SIGNAL OF THE SELECTED BANK IS ASSERTED. тHE BANK SELECTION IS DONE WITH THE TWO SELECT INPUTS с0 AND с1 OF иц1. иц2 AND иц3 FORM A TWO BIT WRITE-ONLY REGISTER, WHOSE OUTPUTS ARE THE BANK SELECT INPUTS TO иц1. бITS 3 AND 4 OF THE реу BANK REGISTER AT $дф06 ARE LATCHED INTO иц2, TWO д TYPE FLIP-FLOPS, ON THE NEGATIVE EDGE OF THE SYSTEM CLOCK (THETA2). бY MAPPING OUR NEW TWO BIT REGISTER TO THESE NORMALLY UNUSED BITS, THE EXTRA MEMORY APPEARS TO THE USER AS EXTRA 64K BANKS BEYOND THE NORMAL MAXIMUM OF 512 KB. иц3 IS A 3 TO 8 LINE DECODER/DEMULTIPLEXOR, WHICH IS USED TO DECODE THE LOWEST THREE BITS OF THE и/о2 PAGE ($дф00 TO $дффф) ADDRESS. тHE иц3 SIGNAL *о6 IS USED AS THE CLOCK SIGNAL FOR THE TWO FLIP-FLOPS, WHICH LATCHES BITS 3 AND 4 OF THE DATA BUS ON THE POSITIVE EDGE. тHIS HAPPENS WHENEVER $дф06 IS WRITTEN TO. оN A READ MEMORY CYCLE TO $дф06, иц3 IS DISABLED AND THE реу'S REGULAR INTERNAL REGISTER APPEARS ON THE DATA BUS. а SWITCH PULLS THE *цлр INPUTS TO EACH OF THE FLIP-FLOPS LOW WHEN IT IS CLOSED (POSITION 1). тHIS FORCES THEM TO SELECT BANK ZERO OF 512 KB AT ALL TIMES, WHICH IS PRESENT IN ALL 512KB реуS. вHEN THE SWITCH IS OPEN (POSITION 2), THE FLIP-FLOPS CAN FREELY TAKE ON THE VALUES OF BITS 3 AND 4 OF $дф06. тHIS ALLOWS COMPLETE SOFTWARE COMPATIBILITY WITH A 1750 (512 KB) реу. лASTLY, THE TWO лIGHT еMITTING дIODES (ледS), WHICH ARE OPTIONAL, SIMPLY SHOW US (IN BINARY) WHAT BANK OF 512K WE ARE USING. тHEY ALLOW US TO QUICKLY CHECK SOFTWARE COMPATIBILITY, AS EXPLAINED LATER. иNSTALLATION ------------ аLL THE EXPANSION HARDWARE FITS INSIDE THE реу CASE. ыOU WILL NOT BE ABLE TO USE THE рф SHIELD, AND IT WILL BE A VERY TIGHT FIT WITH ALL 2 мB INSTALLED (DON'T USE иц SOCKETS!). сTART BY EXPANDING YOUR реу TO 512 KB, OR IN OTHER WORDS YOU NEED A 1750 реу. сEE жOLUME 9, иSSUE 5 OF THE тRANSACTOR, OR THE ARTICLE BY сCOTTб30 ON яUANTUM лINK FOR EXPANDING 1764 AND 1700 реуS. тAKE THE USUAL STATIC PRECAUTIONS, AND OF COURSE, ANY MODIFICATION TO THE реу WILL VOID THE WARRANTY! пROCEED AT YOUR SOLE RISK! оN THE COMPONENT SIDE OF THE реу, WITH THE EDGE CONNECTOR TOWARDS YOU, LOCATE рESISTOR пACKAGE рп3 ON THE LEFT SIDE NEAR THE MIDDLE OF THE BOARD. фLIP THE BOARD OVER TO THE SOLDER SIDE, AGAIN WITH THE EDGE CONNECTOR TOWARDS YOU. лOCATE рп3 AGAIN ON THE RIGHT SIDE OF THE BOARD. фROM THE TOP OF THE BOARD, FIND PIN 7 OF рп3 AND CUT THE TRACE LEADING AWAY FROM THE PIN. сOLDER A WIRE TO THIS PIN (PIN 7); THIS IS THE *цас0 SIGNAL. фIND PIN 3 OF рп3 AND AGAIN CUT THE TRACE LEADING AWAY FROM THE PIN. сOLDER A WIRE TO THIS PIN (PIN 3); THIS IS THE *цас1 SIGNAL. фLIP THE BOARD OVER TO THE COMPONENT SIDE WITH THE EDGE CONNECTOR TOWARDS YOU, AND LOCATE RAM CHIPS у2 AND у10 ON THE TOP LEFT SIDE OF THE BOARD. фLIP THE BOARD OVER TO THE SOLDER SIDE AND AGAIN LOCATE THESE CHIPS. тO PIN 15 OF у2 SOLDER A WIRE; THIS IS THE *цасбанк0 SIGNAL. сOLDER A WIRE TO PIN 15 OF у10; THIS IS THE *цасбанк1 SIGNAL. рUN THE FOUR WIRES YOU NOW HAVE, DOWN TO THE RIGHT SIDE OF THE EDGE CONNECTOR AND SECURE THEM IN THE CORNER WITH A PIECE OF ELECTRICAL TAPE. тHIS COMPLETES ALL THE SOLDER CONNECTIONS TO THE SOLDER SIDE OF THE BOARD. лOCATE THE FIFTH PIN FROM THE RIGHT ON THE EDGE CONNECTOR AND FOLLOW THE TRACE TO A COMPONENT LEG; NOTE THE PLACEMENT. фLIP THE BOARD TO THE COMPONENT SIDE FOR THE LAST TIME, AND LOCATE THE COMPONENT. иT IS LABELED фб2, AND SHOULD BE A фERRITE бUTTON, BUT IS A 430 оHM RESISTOR (YELLOW, ORANGE, BROWN, GOLD BANDS) ON MY реу. тO THE OPPOSITE END OF THE COMPONENT, AWAY FROM THE EDGE CONNECTOR, SOLDER A WIRE; THIS IS THE SYSTEM CLOCK SIGNAL THETA2. лOCATE THE THIRTEENTH PIN FROM THE RIGHT ON THE EDGE CONNECTOR. фOLLOW THE TRACE TO A PASS-THROUGH, AND SOLDER A WIRE INTO IT; THIS IS THE *и/о2 SIGNAL. лOCATE THE EIGHTEENTH PIN FROM THE RIGHT OF THE EDGE CONNECTOR, AND FOLLOW THE TRACE TO фERRITE бUTTON фб1. тO THE SIDE AWAY FROM THE EDGE CONNECTOR SOLDER A WIRE; THIS IS THE р/*в SIGNAL. лOCATE THE EMPTY PINOUT (у18) NEXT TO THE SQUARE рец CHIP. сOLDER WIRES INTO THE HOLES FOR PINS 8, 9, 10, 14, 15, 16, AND 28. тHESE ARE THE SIGNALS а2, а1, а0, гROUND, д3, д4, AND +5 VOLTS RESPECTIVELY. тHIS COMPLETES THE SIGNAL HUNTING. лAY A 2 INCH STRIP OF DOUBLE-SIDED FOAM TAPE DOWN THE CENTER OF THE MISSING иц (у18) PATTERN. тRY TO LEAVE ROOM NEAR THE RIGHT EDGE OF THE CASE SO YOU CAN MOUNT A SWITCH. мOUNT THE ицS, IN ORDER FROM LEFT TO RIGHT, TO THE TAPE упсиде довн (PINS STICKING UP) WITH THE NOTCHES (OR DOTS) TOWARDS THE TOP OF THE BOARD. пLACE THEM AS FAR APART AS YOU CAN ON THE TAPE. нOW CONNECT THE ицS USING (CAREFULLY!) POINT TO POINT SOLDERING, OR WIRE-WRAP дирецтлы ON THE иц PINS (YES, IT CAN BE DONE). иF YOU DO WIRE-WRAP, ONLY 4 WRAPS PER CONNECTION ARE NECESSARY, AND "OVER WRAPPING" (WRAPPING ON TOP OF WRAPPING) IS RECOMMENDED FOR THE SECOND CONNECTION TO A PIN. кEEP THE CONNECTIONS AS SHORT AS POSSIBLE EG. +5 VOLTS TO PIN 14 OF иц1 IN MINE IS 1/4 OF AN INCH LONG. мOUNT THE SWITCH IN THE TOP HALF AND ON THE EDGE OF THE реу'S CASE IN A CONVENIENT PLACE. и RECOMMEND PLACING IT NEAR THE BOTTOM RIGHT CORNER, NEAR THE PLASTIC POST SINCE THERE IS NOTHING IN THE WAY HERE. а SLIDE SWITCH IS NEATER THAN A TOGGLE SWITCH, BUT IT ISN'T VERY MUCH FUN TRYING TO MAKE A SQUARE HOLE FOR A THE SLIDE SWITCH! мARK (OR JUST NOTE) THE POSITION OF THE SWITCH ON THE CASE (OPEN: 2 мB, CLOSED: 512 KB) WITH A MARKER (сANFORD "сHARPIE" WRITES PERMANENTLY ON ANYTHING!) OR USE "лETTRA сET" TYPE LETTERING. тHE NEXT STEP, AND LAST STEP, IS TO WIRE AND MOUNT THE TWO OPTIONAL лед INDICATORS. сOLDER WIRES TO ALL THE LEADS OF BOTH THE ледS. дRILL HOLES FOR THEM AT THE TOP EDGE, OF THE TOP HALF OF THE CASE, SO THEY'RE VISABLE WITH THE реу INSTALLED. мAKE SURE TO PUT лед1 ON THE LEFT AND лед0 ON THE RIGHT, SO YOU CAN READ THE BANK OF 512 KB IN BINARY (0=UN-LIGHTED, 1=LIGHTED). ыOUR реу NOW WORKS THE SAME AS BEFORE, AT LEAST IT SHOULD! пLUG IT IN, MOVE THE SWITCH TO POSITION 1 (SWITCH CLOSED, THE OPTIONAL ледS SHOULD BOTH BE UN-LIGHTED) AND GIVE THE реу A SPIN WITH ANY TEST PROGRAM OF YOUR CHOICE. иF THINGS LOOK BAD, POWER DOWN AND RECHECK ALL CONNECTIONS! иF IT DOES WORK, CONGRATULATIONS! ыOU NOW HAVE AN реу THAT CAN BE EXPANDED TO 2 мB BY ADDING A MEAGER (48) рам CHIPS. аDDING MEMORY ------------- еXPAND THE MEMORY BY PIGGY-BACKING THE EXISTING рам CHIPS IN CHIP BANKS ONE OR TWO, STARTING WITH CHIP BANK 1. бEND PIN 15 UP, TO A 45 DEGREE ANGLE, ON EACH OF THE рам CHIPS TO BE ADDED. цONNECT A WIRE TO THIS PIN BEFORE SOLDERING IT TO THE OTHER рам CHIP. оNCE THE CHIP IS SOLDERED IN PLACE, CONNECT THE WIRE TO PIN 15 OF THE NEXT рам CHIP TO BE ADDED. сOLDER ANOTHER WIRE TO ITS PIN 15, AND SOLDER THE CHIP IN PLACE NEXT TO THE OTHER. цONTINUE IN THIS WAY UNTIL ALL THE рамS IN A CHIP BANK ARE PIGGY-BACKED, AND ALL PINS 15 ARE CONNECTED IN A DAISY-CHAIN FASHION IN EACH CHIP BANK. сOLDER A WIRE TO PIN 15 OF THE RIGHTMOST рам CHIP IN THE BANK; THIS IS THE *цасбанкX SIGNAL. нOW USE AN OHMMETER OR CONTINUITY TESTER TO SEE THAT ALL THE CHIPS IN THE NEWLY ADDED BANK SHARE THE SAME SIGNALS ON PINS 1, 3 TO 13, AND 15 AND 16. аLL THAT IS LEFT IS TO CONNECT THE WIRE *цасбанкX TO AN APPROPRIATE NUMBERED SIGNAL ON иц1. оDD NUMBERED цасбанк SIGNALS ARE FOR рам CHIPS PIGGY-BACKED IN CHIP BANK ONE, EVEN NUMBERED ONES ARE FOR рам CHIPS PIGGY-BACKED IN CHIP BANK TWO. цHOOSE THE NEXT AVAILABLE SIGNAL WHEN ADDING A NEW BANK OF рамS. *цасбанк0 AND *цасбанк1 ARE RESERVED FOR THE TWO CHIP BANKS ALREADY IN A 512 KB реу. цONNECT THE *цасбанкX SIGNAL, AND YOU NOW HAVE ANOTHER 256 KB OF MEMORY! рEPEAT FOR CHIP BANK TWO FOR 512 KB EXTRA рам. аDD JUST AS MUCH рам AS YOU NEED IN 256 KB INCREMENTS! пROGRAMMING AN EXPANDED реу --------------------------- ыOU DON'T NEED TO DO ANYTHING DIFFERENT TO USE THE EXTRA MEMORY IN THE реу. йUST REMEMBER THAT YOU NOW HAVE MORE 64 KB BANKS THAT YOU CAN ACCESS THROUGH THE BANK REGISTER AT $дф06 WHEN IN 2 мB MODE (SWITCH IN POSITION 2). вHEN IN THE 1750 EMULATION (512 KB) MODE (SWITCH IN POSITION 1), REMEMBER YOU ONLY HAVE ACCESS TO BANKS 0 TO 7 OF 64 KB. кEEP IN MIND THE PECULIARITIES OF THE 2 мB MODE AS WELL. тHAT'S ALL THERE IS TO IT! тHE NUMBER OF BANKS DEPENDS ON HOW MUCH MEMORY YOU ADDED; 0 TO 15 WITH 1 мB, AND 0 TO 31 WITH 2 мB FOR EXAMPLE. нOTE THAT ALL SOFTWARE THAT TESTS FOR A реу WILL ONLY FIND 512 KB AVAILABLE, SO A SLIGHTLY DIFFERENT MEMORY TEST IS NECESSARY TO CHECK ON HOW MUCH EXPANSION MEMORY WE HAVE. сINCE THE реу CAN BE EXPANDED UP TO 2 мB IN 256 KB INCREMENTS AT THE USERS DISCRETION, A SLIGHTLY DIFFERENT TEST IS MANDATORY TO FIGURE OUT JUST HOW BIG THE реу IS. сEE LISTING 1 FOR AN EXAMPLE. пECULIARITIES ------------- тHERE ARE A FEW VERY MINOR INCONVENIENCES WITH THIS EXPANSION PROJECT DETAILED AS FOLLOWS: 1) тHE реу WILL NOT WRAP INTERNALLY BETWEEN BANKS OF 512 KB, INSTEAD THE реу WILL WRAP TO THE BEGINNING OF THE SAME 512K BANK. фOR EXAMPLE, SAVING 2 BYTES TO $фффф IN BANK 7 WILL PUT ONE BYTE AT $фффф IN BANK 7, AND THE OTHER AT $0000 IN BANK 0 нот BANK 8 AS EXPECTED. тHIS IS BECAUSE THE рец CHIP DOES NOT RECOGNIZE MORE THAN 512 KB DIRECTLY; WE HAVE FOOLED IT TO USE MORE рам. 2) бANK REGISTER AT $дф06 IS WRITE-ONLY WHERE BITS 3 AND 4 ARE CONCERNED. иF $дф06 IS READ, BITS 3 AND 4 (AS WELL AS BITS 5, 6, AND 7) WILL ALWAYS BE ONE NO MATTER WHAT BANK OF 512 KB THE реу IS IN. 3) бITS 3 AND 4 OF THE BANK REGISTER AT $дф06 ARE NOW SIGNIFICANT, BUT IN AN UNEXPANDED реу THEY ARE IGNORED. тHIS WHY WE HAVE A SWITCH TO DISABLE ALL BUT 512K OF MEMORY WHEN WE RUN INTO NON-COMPATIBLE SOFTWARE. сEE THE NEXT SECTION FOR DETAILS. 4) тHE 512 KB BANK SELECT BITS ARE MEMORY MAPPED BY ONLY THE THREE LOWEST ADDRESS BITS. тHIS MEANS THERE ARE IMAGES OF THESE BITS AT $дф0е, $дф16, $дф1е, ETC. тHIS IS A TRIVIAL MATTER SINCE NO SANE PERSON USES IMAGE ADDRESSES! цOMPATIBILITY ------------- тHERE IS ONLY ONE SOURCE OF SOFTWARE INCOMPATIBILITY IN THIS MODIFICATION; THE 2 BIT 512 KB BANK SELECT REGISTER WE HAD ADDED TO $дф06. сINCE THESE TWO BITS ARE NOW SIGNIFICANT AND DIDN'T USED TO BE, WE COULD HAVE A PROBLEM; SOFTWARE THAT DOESN'T SET THESE BITS TO THE SAME VALUE AT ALL TIMES, OR SETS THE BITS TO A BANK OF 512 KB THAT ISN'T INSTALLED YET, WON'T WORK. бUT THIS IS WHAT THE SWITCH IS FOR! тHE 2 мB MODIFICATION IS 100% COMPATIBLE WITH ANY SOFTWARE WRITTEN FOR A 1750 (512KB) реу, WHEN IN THE SWITCH SELECTABLE 1750 EMULATION MODE (POSITION 1, SWITCH CLOSED). уNFORTUNATELY NONE OF THE EXTRA MEMORY BEYOND THIS CAN BE ACCESSED WHEN IN THIS MODE. тHIS IS OF NO CONSEQUENCE, SINCE THE SOFTWARE CAN'T MAKE USE OF ANY ADDITIONAL MEMORY ANYWAY. вHEN THE 2 мB MODE IS SWITCH SELECTED (POSITION 2, SWITCH OPEN), WE HAVE COMPLETE ACCESS TO HOW EVER MUCH MEMORY WE HAVE ADDED. тHE SWITCH SHOULD BE IN POSITION 2 WHENEVER POSSIBLE! мOST SOFTWARE CAN FUNCTION IN THIS MODE, INCLUDING геос! тHE TWO OPTIONAL ледS ARE VERY USEFUL TO DETERMINE IF THE SOFTWARE IS COMPATIBLE IN THE 2 мB MODE. иF YOU ARE USING SOFTWARE MEANT TO BE USED WITH A 1750 реу, YOU CAN USE THE SOFTWARE IN THE 2 мB MODE IF: DURING A реу TRANSFER THE ледS ARE ALWAYS SHOWING THE SAME BANK OF 512 KB IS BEING ACCESSED (ледS NOT FLICKERING), AND THEY INDICATE A BANK THAT IS INSTALLED (BANK 0 OF 512 KB IS ALWAYS PRESENT). вITHOUT THE ледS, IT IS SIMPLY A MATTER OF SAYING "иT WORKS", OR "иT DOESN'T WORK" WHEN YOU USE SOFTWARE FOR A 1750 реу. фINAL WORDS ----------- дON'T LET THE LENGTH OF THIS ARTICLE DISCOURAGE YOU; IT ONLY SEEMS DIFFICULT IN PRINT! ыOUR реу CAN NOW CONTAIN MORE MEMORY THAN AN AVERAGE ибм пц. сO BE NICE TO YOUR ибм BUDDIES, AND DON'T BRAG TOO MUCH! и CAN BE REACHED ON я-LINK (SCREEN NAME рECURSION), OR YOU CAN WRITE ME DIRECTLY IF YOU HAVE ANY QUESTIONS, COMMENTS, OR CONSTRUCTION IDEAS. аNDREW е. мILESKI 210-180 лEES аVENUE оTTAWA, оNTARIO цANADA, к1с 5й6 лISTING 1: рECOMMENDED TYPE OF реу MEMORY CHECK ----------------------------------------------- иT IS IMPLIMENTED HERE IN басиц WITH A реу WEDGE FOR THE ц64, BUT CAN EASILY BE TRANSLATED INTO ASSEMBLY. тHIS CHECK WILL ALWAYS RETURN THE NUMBER OF 64 K BYTE BANKS THAT ARE USEABLE IN THE реу. фетцх AND стасх DO EXACTLY WHAT YOU MIGHT THINK. тHE OPERANDS ARE BYTES TO TRANSFER, COMPUTER BASE ADDRESS, реу BASE ADDRESS, AND реу BANK (OF 64 KB) NUMBER. 2000 рем ****инитиализе **** 2010 рем пUT A SINGLE STATUS BYTE, THAT SHOWS AN UNCHECKED BANK, IN EACH BANK OF 64KB. 2020 поке 49152,136 2030 фор и=0 то 255 2040 !стасх 1,49152,0,и 2050 неьт 2060 рем **** тест **** 2070 рем тEST FOR # BANKS PRESENT BY SEEING IF BANK CHECKED YET. иF NOT, CHANGE STATUS OF 2080 рем BANK TO CHECKED, AND ADD 1 TO THE # OF BANKS. еLSE, BANK IS CHECKED ALREADY AND 2090 рем WE'RE DONE! нOTE THAT WE ONLY TEST ONE BYTE PER BANK TO SPEED THINGS UP. 2100 поке 49152,27 2110 и=0 2120 !фетцх 1,49152,0,и 2130 иф пеек(49152)<>136 тхен 2190 2140 поке 49152,27 2150 !стасх 1,49152,0,и 2160 и=и+1:иф и<256 тхен 2120 2170 рем **** доне **** 2180 рем нUMBER OF BANKS OF 64KB IS NOW IN и. 2190 иф и=0 тхен принт "реу нот пресент, ор нот сеатед проперлы" 2200 иф и=2 тхен принт "тхис ис а 1700 (128 к) реу" 2210 иф и=4 тхен принт "тхис ис а 1764 (256 к) реу" 2220 иф и=8 тхен принт "тхис ис а 1750 (512 к) реу" 2230 иф и>8 тхен принт "тхис ис ан еьпандед"; 64*и ;"к реу" пARTS лIST AND мISCELLANEOUS дATA --------------------------------- рEQUIRED PARTS иц1: 74ф139 дUAL 2 TO 4 LINE DECODER/DEMULTIPLEXOR. иц2: 74ф74 дUAL д-TYPE FLIP-FLOPS. иц3: 74ф138 3 TO 8 LINE DECODER/DEMULTIPLEXOR. фаст SERIES COMPONENTS RECOMMENDED! 3.3K оHM рESISTOR, 1/4 WATT AND 5% TOLERANCE. спст MICRO-MINI TOGGLE, OR SLIDE SWITCH. тWO INCH STRIP OF DOUBLE-SIDED FOAM TAPE. сUPPLY OF 30 GAUGE WIRE. аND OTHER STANDARD TOOLS AND EQUIPMENT. оPTIONAL тWO ледS т-1 SIZE. тWO 390 оHM RESISTORS, 1/4 WATT AND 5% TOLERANCE. пIN CONNECTIONS --------------- иц1 пIN 16: +5 жOLTS 1: *цас0 15: *цас1 2: иц2 PIN 5 14: иц1 PIN 2 3: иц2 PIN 9 13: иц1 PIN 3 4: *цасбанк0 12: *цасбанк1 5: *цасбанк2 11: *цасбанк3 6: *цасбанк4 10: *цасбанк5 7: *цасбанк6 9: *цасбанк7 8: гROUND иц2 пIN 14: +5 жOLTS 1: **1** 13: **1** 2: д3 12: д4 3: иц3 PIN 9 11: иц2 PIN 3 4: +5 жOLTS 10: +5 жOLTS 5: иц1 PINS 2,14 9: иц1 PINS 3,13 6: лед0 **2** 8: лед1 **2** 7: гROUND иц3 пIN 16: +5 жOLTS 1: а0 15: нO CONNECTION 2: а1 14: нO CONNECTION 3: а2 13: нO CONNECTION 4: *и/о 12: нO CONNECTION 5: р/*в 11: нO CONNECTION 6: тHETA2 10: нO CONNECTION 7: нO CONNECTION 9: иц2 PINS 3,11 8: гROUND **1** цONNECT THIS PIN TO ONE SIDE OF THE SWITCH. тHERE SHOULD BE TWO PINS CONNECTED TO THE SAME SIDE OF THE SWITCH. тO THE SAME SIDE OF THE SWITCH CONNECT A SINGLE 3.3K оHM RESISTOR. цONNECT THE FREE END OF THE RESITOR TO +5 жOLTS. цONNECT THE OTHER SIDE OF THE SWITCH TO GROUND. **2** цONNECT THIS PIN TO THE CATHODE OF THE лед SHOWN. цONNECT THE ANODE OF EACH лед TO ITS OWN 390 оHM RESISTOR. цONNECT THE FREE END OF EACH RESISTOR TO +5 жOLTS. тOP OF ицS ARE INDICATED BY A DOT OR NOTCH. вHEN THE CHIPS ARE INSTALLED UP-SIDE-DOWN, THE PIN NUMBERING IS CLOCKWISE FROM THE TOP RIGHT PIN! сINCE THE рам CHIPS ARE INSTALLED RIGHT-SIDE UP, THEIR PIN NUMBERING IS COUNTER CLOCKWISE FROM THE TOP LEFT PIN. дON'T MIX UP THE NUMBERING!!! ***нOTE*** тHIS FILE WAS CONVERTED FROM THE ORIGINAL GEOвRITE 2.1 FILE BY THE AUTHOR. тHE SCHEMATIC IN GEOпAINT FORMAT HAS BEEN REDUCED INTO THE PIN CONNECTION TABLE SHOWN ABOVE. иF YOU HAVE геос 2.0 и RECOMMEND YOU OBTAIN THE ORIGINAL арцED FILES FROM я-лINK ("беыонд512кб.сда" BY рECURSION)