------------------------------
     -ÈOW TO ADD 32K ÒÁÍ TO A 1541-
     ------------------------------

ÆILENAME: "EXPAND1541/32K"

         ÂY ÁNDREW Å. ÍILESKI
         "ÒECURSION" ON Ñ-ÌINK
         210-180 ÌEES ÁVENUE
         ÏTTAWA, ÏNTARIO
         ÃANADA Ë1Ó 5Ê6

             ÃOPYRIGHT
           ÍARCH 24, 1990


ÎOTE: ÔHIS IS FOR EXPERIENCED HARDWARE
----- HACKERS ONLY! ÐROCEED ENTIRELY AT
      YOUR OWN RISK, AND YOU CAN KISS
      THE WARRANTY GOODBYE!

ÔHIS IS BASED ON A 1984 ÒEVISION Á
CIRCUIT BOARD, BUT THERE SHOULD BE
ENOUGH INFO HERE TO DO THE EXPANSION ON
ANY 1541 DRIVE WITH VERY LITTLE WORK,
AND ONLY A LITTLE THOUGHT.

ÈINTS FOR OTHER VERSIONS OF CONTROLLER
BOARDS: ÆIGURE OUT WHICH ÒÏÍ IS ÒÏÍ0
($Ã000-$ÄÆÆÆ) AND ÒÏÍ1 ($Å000-$ÆÆÆÆ).
ÙOU ÍÁÙ HAVE TO BEND PIN 20 OF EACH
ÒÏÍ 180 DEGREES TO THE VERTICAL; THIS
IS THE *ÒÏÍX PIN. ÉGNORE STEPS 13, 14,
15, AND 16.

ÔHIS MAY NOT BE THE EASIEST OR BEST WAY
TO ADD ÒÁÍ, BUT IT DOES WORK. ÓERIOUSLY
CONSIDER BUYING ONE OF THE ÒÁÍ BOARDS
ON THE MARKET TODAY. ÔHEY ARE EASY TO
INSTALL.

!!!!!!!!!!!!!!!×ÁÒÎÉÎÇ!!!!!!!!!!!!!!!!!
ÙOU'LL BE HANDLING VERY ÅÓÄ SESITIVE
DEVICES! ÍAKE SURE YOU AND YOUR TOOLS
ARE PROPERLY GROUNDED AT ALL TIMES!
(ÉF YOU DON'T KNOW WHAT ÅÓÄ STANDS FOR,
DON'T EVEN THINK ABOUT TRYING THIS!!)
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

ÁN ASTERISK * BEFORE A SIGNAL MEANS IT
IS ACTIVE LOW.

ÆEEL FREE TO CONTACT ME IF YOU NEED
SOME HELP, OR HAVE A PROJECT IDEA.
(ÉF IT WAS NOT FOR ÒAYMONDÄ2 ON Ñ-LINK
ASKING HOW TO ADD 8K TO HIS 1541, É
NEVER WOULD HAVE WRITTEN THIS FILE!
ÔHANKS ÒAYMOND!)

ÎOTE: É DID THE 8K MODIFICATION ON MY
OWN DRIVE. ÉT DOES WORK. É MODIFIED IT
SLIGHTLY; É NOW HAVE 32K ÒÁÍ INSTALLED!

***************************************
ÈOW IT WORKS
------------

ÔHE 1541 IS VERY SLOPPY ABOUT HOW IT
USES ITS 64K MEMORY SPACE. ÔHE FIRST
32K ($0000-$7ÆÆÆ) IS RESERVED FOR THE
ÒÁÍ AND É/Ï CHIPS. ÔHIS IS 2048+2*15
BYTES NEEDED, BUT ALMOST 30K WASTED!
ÔHE SECOND 32K ($8000-$ÆÆÆÆ) IS FOR THE
16K OF ÒÏÍS, WHICH MEANS ANOTHER 16K
HAS BEEN WASTED! ÓO, WE CLEAN UP THE
MEMORY MAP, AND USE 32K OF THE WASTED
46K TO ADD SOME MORE ÒÁÍ! ÔHIS WASTES
ONLY 14K. É DARE ANYONE TO TRY TO ADD
40K OF MEMORY :)

ÔHE NITTY-GRITTY DETAILS
------------------------

ÉÃ1 DECODES THE 64K ADDRESS SPACE OF
THE 6502 INTO FOUR 16K SEGMENTS. ÔHE
FIRST SEGMENT ($0000-$3ÆÆÆ) IS RESERVED
FOR THE DRIVES OWN MEMORY AND É/Ï. ÔHIS
IS DONE BY GENERATING A FAKE Á15 SIGNAL
WHICH É CALL ÆÁ15. ×E ALLOW THIS SIGNAL
TO GO LOW (LOGIC 0) ONLY WHEN WE NEED
THE INTERNAL 2K ÒÁÍ AND É/Ï CHIPS.

ÔHE NEXT TWO SEGMENTS ($4000-$ÂÆÆÆ) ARE
OUR 32K EXPANSION ÒÁÍ AREA. ÁN ÁÎÄ GATE
IS FORMED WITH ÒÄÌ (RESISTOR AND DIODE
LOGIC) TO JOIN THE 16K SEGMENTS.

ÔHE LAST 16K SEGMENT IS RESERVED FOR
THE DRIVE'S ÒÏÍS, AND IS UNUSED ON ÉÃ1.

ÉÃ2 DECODES THE 64K ADDRESS SPACE INTO
8 MEMORY SEGMENTS OF 8K. ÔHE LAST TWO
SEGMENTS ($Ã000-$ÄÆÆÆ, $Å000-$ÆÆÆÆ) ARE
FOR ÒÏÍ0 AND ÒÏÍ1 RESPECTIVELY. ÔHE ÉÃ
IS ENABLED ONLY ON READ CYCLES.

×HY THIS WAY?
-------------

ÎOTE THAT É DIDN'T HAVE ANY SCHEMATICS
FOR THE 1541, SO THIS METHOD IS MOST
LIKELY NOT THE BEST. É ALSO DIDN'T HAVE
A VERY WIDE SELECTION OF ÉÃS ON HAND AT
THE TIME, SO É USED WHAT É HAD!

ÉN OTHER WORDS, IF YOU KNOW OF A BETTER
METHOD SHARE IT WITH THE REST OF US!
***************************************
 1) ÄECIDE TO ADD 8K OR 32K. ÍOST OF
    TODAYS SOFTWARE USES ONLY 8K, BUT
    WHO KNOWS WHAT MAY BE IN STORE FOR
    THE FUTURE! ÆOR 8K, IGNORE THIS
    ARTICLE, AND READ THE FILE
    "EXPAND1541/8K".
 2) ÏBTAIN THE PARTS:
    ÔWO 74ÌÓ138 (3 TO 8 LINE DECODER)
    ÏNE 62256 (32K STATIC ÒÁÍ, 120NS)
    (NOTE THAT A 62ÌÐ256 IS LOW-POWER)
    ÔWO SWITCHING DIODES (ANY WILL DO)
    ÏNE 3.3K ÏHM 1/4 ×ATT RESISTOR.
    Á SMALL PIECE OF PRE-DRILLED BOARD.
    ÔWO 16 PIN WIRE-WRAP SOCKETS IF YOU
    ARE GOING TO WIRE-WRAP THE CIRCUIT.
 3) ÏPEN THE DISK DRIVE CASE AND REMOVE
    THE ÒÆ SHEILD.
 4) ÍARK ONE END OF ÁÌÌ CONNECTORS WITH
    A MARKER, SO THAT YOU WILL BE ABLE
    TO REPLACE THEM LATER.
 5) ÕNPLUG ÁÌÌ CONNECTORS.
 6) ÕNSCREW THE CIRCUIT BOARD. ÄON'T
    FORGET THE SCREWS THAT ATTACH THE
    HEATSINK TO THE FRAME.
 7) ÌIFT THE CIRCUIT BOARD OUT OF THE
    DISK DRIVE AND PLACE IT ON YOUR
    ANTI-STATIC CONDUCTIVE MAT (OR IF
    YOUR DESPERATE, A FOLDED TOWEL
    WILL DO!) COMPONENT SIDE UP, AND
    IN THE SAME ORIENTATION (TOP OF
    BOARD IS TOWARDS BACK OF DRIVE).
 8) ÆIND THE 6116 (2K BY 8 BIT ÒÁÍ) ON
    THE CIRCUIT BOARD (24 PINS AND NOT
    SOCKETED, LEFT SIDE AT THE BACK).
 9) ÏN THE NEW ÒÁÍ CHIP TO BE ADDED
    CAREFULLY BEND THE FOLLOWING PINS
    180 DEGREES, SO THAT THEY ARE
    POINTING IN THE OPPOSITE DIRECTION:
    PIN 1, 2, 20, 22, 23, 26, 27, AND
    28. ÔHESE ARE THE SIGNALS Á13, Á12,
    *ÃÓ, *ÏÅ, Á11, Á14, *×Å AND +5
    VOLTS.
10) ÓIT THE NEW ÒÁÍ CHIP ON TOP OF THE
    6116 CHIP. ÔHE BOTTOM PINS SHOULD
    BE ALIGNED. ÍAKE SURE THAT BOTH OF
    THE CHIPS HAVE THEIR TOP-OF-CHIP
    REFERENCE MARKS POINTING IN THE
    SAME DIRECTION.
11) ÃAREFULLY SOLDER THE TWO CHIPS PINS
    TOGETHER SO THEY ARE PIGGY-BACKED.
    ÂE CAREFULL TO AVOID SOLDER BRIDGES
    BETWEEN PINS.
12) ÌOCATE THE TWO 8K ÒÏÍ CHIPS ON THE
    CIRCUIT BOARD (24 PINS AND SOCKETED
    ON RIGHT OF 6116).
13) ÔO THE RIGHT OF THE ÒÏÍS, BETWEEN
    THE CHIPS AND THE HEATSINK, YOU
    WILL SEE 3 SILVER DOTS ON THE ÐÃÂ.
    ÔHESE ARE PASS-THROUGHS TO THE
    OTHER SIDE OF THE BOARD.
14) ÆLIP THE BOARD OVER, AND AGAIN FIND
    THE SAME 3 PASS-THROUGHS.
15) ÃUT THE TRACE LEADING TO THE FRONT
    TWO PASS-THROUGHS (THE ONES TOWARDS
    THE FRONT OF THE DRIVE).
    ÔHE SIGNALS *ÒÏÍ0 AND *ÒÏÍ1 REPLACE
    THE ORIGINAL ÒÏÍ CHIP SELECTS THAT
    GO TO PIN 20 OF THE ÒÏÍS, THAT IS
    WHY YOU MUST CUT THE TRACES!
16) ÓOLDER A WIRE INTO THE FRONT PASS-
    THROUGH; THIS ISàTHE *ÒÏÍ0 SIGNAL
    ÓOLDER A WIRE INTO THE MIDDLE
    PASS-THROUGH; THIS IS THE *ÒÏÍ1
    SIGNAL. ÔHE WIRES SHOULD BE LONG
    ENOUGH TO REACH THE FRONT OF THE
    BOARD PLUS ABOUT FOUR INCHES.
17) ÆIND THE 6502 ÃÐÕ CHIP (40 PINS)
    ON THE SOLDER SIDE OF THE BOARD.        ÓOLDER WIRES TO PINS 8, 20, 21, 22,
    23, 24, 25,AND 34. ÔHESE ARE THE
    SIGNALS +5 VOLTS, Á11, GROUND, Á12,
    Á13, Á14, Á15, AND Ò/*×. ÓOLDER TWO
    WIRES TO 23, 24, AND 34 SO YOU CAN
    CONNECT THE 62256 ÒÁÍ CHIP.
18) ÏN THE COMPONENT SIDE OF THE BOARD
    AGAIN WITH THE 6502. ÌOCATE PIN 25
    (Á15). ÆOLLOW THE TRACE LEADING
    FROM THE PIN TO A PASS-THROUGH.
    ÃUT THE TRACE. ÆLIP THE BOARD OVER
    AND LOCATE THE PASS-THROUGH AGAIN.
    ÓOLDER A WIRE INTO IT; THIS IS THE
    ÆÁ15 SIGNAL.
19) ÏN A SMALL (1.25X1.75 INCH) PIECE
    OF CIRCUIT BOARD, WIRE-WRAP THE ÉÃS
    OR USE POINT-TO-PONT SOLDERING.

    ÉÃ1, A 74ÌÓ138
    PIN
    1 Á14          16 +5 VOLTS
    2 Á15          15 ÆÁ15
    3 ÇROUND       14 ÄIODE1
    4 ÇROUND       13 ÄIODE2
    5 ÇROUND       12
    6 +5 VOLTS     11
    7              10
    8 ÇROUND        9

    ÉÃ2, A 74ÌÓ138
    PIN
    1  Á13         16 +5 VOLTS
    2  Á14         15
    3  Á15         14
    4  ÇROUND      13
    5  ÇROUND      12
    6  Ò/*×        11
    7  *ÒÏÍ1       10
    8 ÇROUND        9  *ÒÏÍ0

    ÄIODE1 AND ÄIODE2 ARE THE CATHODE
    ENDS (MARKED ON DIODE WITH A BAND).
    ÃONNECT THE ANODES (OTHER END) OF
    EACH DIODE TOGETHER AND TO A WIRE,
    AND ALSO TO THE SAME END OF THE
    RESISTOR; THE WIRE IS THE *ÃÓ
    SIGNAL FOR THE 62256. ÔO THE
    OPPOSITE END OF THE RESISTOR (THE
    END THAT ISN'T CONNECTED TO
    ANYTHING YET), CONNECT +5 VOLTS.

    ÌOOKS LIKE THIS:
                         *ÃÓ
               ÄIODE1     ^
ÉÃ1 PIN 14 _ÀÀÀÀÜæææÀÀÀÀî Ý
                        ëÀñÀØØØØÀÀ> +5Ö
ÉÃ1 PIN 13 _ÀÀÀÀÜæææÀÀÀÀý RESISTOR
               ÄIODE2

20) ÃONNECT THE 6502, ÒÏÍS, AND ÒÁÍ
    CHIP SIGNALS TO THE 74ÌÓ138S.
    ÒUN THE WIRES TO THE FRONT, RIGHT
    OF THE BOARD (SEE BELOW FOR ÒÁÍ).

    ÃONNECT ÒÁÍ PIN 1 (Á13) TO THE 6502
    PIN 23 (Á13) WIRE.
    ÃONNECT ÒÁÍ PIN 2 (Á12) TO THE 6502
    PIN 22 (Á12) WIRE.
    ÃONNECT ÒÁÍ PIN 20 (*ÃÓ) TO THE ÒÄÌ
    "ÁÎÄ" GATE AS DESCRIBED IN STEP 19.
    ÃONNECT ÒÁÍ PIN 22 (*ÏÅ) TO PIN 14
    (ÇROUND) OF THE CHIP WITH A SMALL
    WIRE.
    ÃONNECT ÒÁÍ PIN 23 (Á11) TO THE
    6502 PIN 20 (Á11) WIRE.
    ÃONNECT ÒÁÍ PIN 26 (Á15) TO THE
    6502 PIN 24 (Á14) WIRE.
    ÃONNECT ÒÁÍ PIN 27 (*×Å) TO THE
    6502 PIN 34 (Ò/*×) WIRE.
    ÃONNECT ÒÁÍ PIN 28 (+5 ÖOLTS) TO
    6116 PIN 24 WITH A SMALL WIRE.

    ÒUN THESE WIRES TO THE LEFT OF THE
    BOARD, AND AROUND TO THE SOLDER
    SIDE.

21) ÒEPLACE THE DRIVE CONTROLLER BOARD
    IN THE DRIVE, AND MOUNT THE NEW
    SMALL CIRCUIT BOARD TO THE FRAME
    WITH A SMALL MACHINE SCREW.
22) ÂÅÆÏÒÅ YOU SCREW THE DRIVE BOARD IN
    PLACE, MAKE SURE THE WIRES ARE NOT
    NEAR THE DRIVE OR TRANSFORMER, AND
    TAPE THEM IN PLACE TO THE BOTTOM OF
    THE BOARD.
23) ÓCREW THE DRIVE CONTROLLER BOARD TO
    THE FRAME AGAIN.
24) ÐLUG IN ALL THE CONNECTORS AGAIN.
    ÃHECK YOUR REFERENCE MARKS.
25) ÐLUG THE DRIVE IN, AND TEST TO MAKE
    SURE THE DRIVE STILL WORKS NORMALLY
26) ÉF OKAY, THEN REPLACE ÒÆ SHIELD AND
    CASE COVER. ÉF NOT, POWER-DOWN AND
    CHECK ALL YOUR CONNECTIONS!
27) ÐAT YOUSELF ON THE BACK, YOUR DONE!
    ÙOU KNOW HAVE 32K ÒÁÍ EXTRA!

    ÔHE 32K YOU INSTALLED IS AVAILABLE
    AT $4000-$ÂÆÆÆ

    ÒÏÍ0 AVAILABLE AT: $Ã000-$ÄÆÆÆ
    ÒÏÍ1 AVAILABLE AT: $Å000-$ÆÆÆÆ
    ÔHE ÒÏÍS ARE READ ONLY, AS THEY
    SHOULD BE.
***************************************