-----------------------------
     -ÈOW TO ADD 8K ÒÁÍ TO A 1541-
     -----------------------------

ÆILENAME: "EXPAND1541/8K"

         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 THIS MODIFICATION ON MY
OWN DRIVE. ÉT DOES WORK. É MODIFIED IT
SLIGHTLY; É NOW HAVE 32K ÒÁÍ INSTALLED!

***************************************
 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 32K, IGNORE THIS
    ARTICLE, AND READ THE FILE
    "EXPAND1541/32K".
 2) ÏBTAIN THE PARTS:
    ÔWO 74ÌÓ138 (3 TO 8 LINE DECODER)
    ÏNE 6264 (8K STATIC ÒÁÍ, 120NS)
    (NOTE THAT A 62ÌÐ64 IS LOW-POWER)
    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 2, 20, 22, 23, 27, AND 28.
    ÔHESE ARE THE SIGNALS Á12, *ÃÓ,*ÏÅ,
    Á11, *×Å AND +5 VOLTS.
    ÂREAK OFF PIN 1; WE DON'T NEED IT.
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
    2 PASS-THROUGHS (THE ONES TOWARDS
    THE FRONT OF THE DRIVE). ÔHE *ÒÏÍ0
    AND *ÒÏÍ1 SIGNALS REPLACE THE
    ORIGINAL ÒÏÍ CHIP SELECTS THAT GO
    TO PIN 20 ON 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 RIGHT OF THE BOARD).  ÓOLDER
    WIRES TO PINS 8, 20, 21, 22, 23,
    24, 25, 34 AND 39. ÔHESE ARE THE
    SIGNALS +5 VOLTS, Á11, GROUND, Á12,
    Á13, Á14, Á15, Ò/*×, AND THETA2.
    ÓOLDER TWO WIRES TO PIN 34 SO YOU
    CAN CONNECT THE ÒÁÍ CHIP.
18) ÏN A SMALL (1.25X1.75 INCH) PIECE
    OF CIRCUIT BOARD, WIRE-WRAP THE ÉÃS
    OR USE POINT-TO-POINT SOLDERING.

    ÉÃ1, A 74ÌÓ138
    PIN
    1  Á14         16 +5 VOLTS
    2  Á15         15
    3  ÇROUND      14
    4  ÇROUND      13 6264 PIN 20
    5  ÇROUND      12 ÉÃ2 PIN 4
    6  ÔHETA2      11
    7              10
    8  ÇROUND       9

    ÉÃ2, A 74ÌÓ138
    PIN
    1  Á13         16 +5 VOLTS
    2  ÇROUND      15 *ÒÏÍ0
    3  ÇROUND      14 *ÒÏÍ1
    4  ÉÃ1 PIN 12  13
    5  ÇROUND      12
    6  Ò/*×        11
    7              10
    8 ÇROUND        9

19) 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 2 (Á12) TO THE 6502
    PIN 22 (Á12) WIRE.
    ÃONNECT ÒÁÍ PIN 20 (*ÃÓ) TO ÉÃ1 PIN
    13 (*ÃÓ).
    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 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.

20) ÒEPLACE THE DRIVE CONTROLLER BOARD
    IN THE DRIVE, AND MOUNT THE NEW
    SMALL CIRCUIT BOARD TO THE FRAME
    WITH A SMALL MACHINE SCREW.
21) 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.
22) ÓCREW THE DRIVE CONTROLLER BOARD TO
    THE FRAME AGAIN.
23) ÐLUG IN ALL THE CONNECTORS AGAIN.
    ÃHECK YOUR REFERENCE MARKS.
24) ÐLUG THE DRIVE IN, AND TEST TO MAKE
    SURE THE DRIVE STILL WORKS NORMALLY
25) ÉF OKAY, THEN REPLACE ÒÆ SHIELD AND
    CASE COVER. ÉF NOT, POWER-DOWN AND
    CHECK ALL YOUR CONNECTIONS!
26) ÐAT YOUSELF ON THE BACK, YOUR DONE!
    ÙOU KNOW HAVE 8K ÒÁÍ EXTRA!

    ÔHE 8K YOU INSTALLED IS AVAILABLE
    AT $8000-$ÂÆÆÆ (A 16K SEGMENT)
    ÆOR EXAMPLE:
    $8000-$9ÆÆÆ,$9000-$ÁÆÆÆ,$A000-$ÂÆÆÆ
    ×ILL ALL GIVE YOU ACCESS TO THE
    SAME 8K OF ÒÁÍ.

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

ÉÃ1 DECODES THE 64K ADDRESS SPACE OF
THE 6502 INTO FOUR 16K SEGMENTS, AND
ALSO SYNCHRONIZES TO THE SYSTEM CLOCK
THETA2. ÔHIS ÉÃ SELECTS THE ÒÁÍ CHIP
DIRECTLY.

ÉÃ2 DECODES ONE OF THE ABOVE MENTIONED
16K MEMORY SEGMENT TO TWO 8K SEGMENTS,
AND ONLY ALLOWS READ CYCLES TO OCCUR.
ÔHIS ÉÃ SELECTS EACH ÒÏÍ CHIP.

×HY THIS WAY?
-------------

É DID THINGS THIS WAY SO THAT THE 8K
OF EXTRA ÒÁÍ WOULD BE AVAILABLE IN
THE LARGEST SEGMENT OF MEMORY POSSIBLE.
ÔHIS IS TO ALLOW COMPATIBLITY WITH AS
MUCH SOFTWARE AS POSSIBLE.

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!
***************************************