111 lines
4.1 KiB
Plaintext
111 lines
4.1 KiB
Plaintext
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#53 2 20 Jul 86 17:49:12
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From: David James
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To: All
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Subj: Upgrade IBM Memory Sidecar to 512K
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ALTERING THE IBM PCJR 128 MEMORY MODULE
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TO 512K
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The following instructions will show you how to alter
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your IBM PCJR side mounted 128k memory module to 512k. this
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of course will give a potent 640k machine providing you have
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the later release of the 128k and not the 64k original.
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You must be able to use a soldering iron and be able to
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de-solder connections. I am not an expert with a soldering
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iron but I found just being careful and taking my time I was
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able to complete the operation in about four hours without
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damaging my board or components as I have heard others have
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done.
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An important factor in my wanting to make this
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alteration was the obvious cost. total parts cost for me was
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More?
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approx. $70.00. I understand that the parts may be purchased
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cheaper elsewhere so you may want to shop around. If you have
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been hungry for more memory in your JR and saw the prices for
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commercial memory expansions you can see that you will save
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up to $400.00 by doing this operation.
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STEPS
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1. REMOVE THE 128K MEMORY BOARD FROM THE MODULE. HOLD THE
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COMPONENT SIDE TOWARDS YOU AND LOOK FOR 16 CHIPS MOUNTED IN A
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ROW VERTICALLY ALONG ONE OF THE LONG EDGES OF THE BOARD.
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THESE CHIPS WILL ALSO HAVE THE SAME NUMBER ON THEM. THESE ARE
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THE 16 CHIPS YOU WILL REMOVE.
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2. CAREFULLY UNSOLDER AND REMOVE THESE CHIPS. BE VERY CAREFUL
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NOT TO ALLOW SOLDER TO GET ON OTHER COMPONENTS, IF IT DOES,
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REMOVE IT. ALSO BE CAREFUL ABOUT SCRATCHING THE BOARD AS YOU
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MAY DISCONNECT A PRINTED CIRCUT FROM A COMPONENT.
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3. NOW BEFORE YOU REPLACE THE CHIPS YOU JUST REMOVED I HIGHLY
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RECOMMEND YOU INSTALL 16 PIN SOCKETS WHERE YOU JUST REMOVED
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EACH CHIP FROM. THESE SOCKETS ARE VERY INEXPENSIVE AND WILL
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ALLOW YOU TO PLACE THE NEW LARGER CAPACITY CHIPS ON THE BOARD
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WITHOUT EXPOSING THEM TO THE HEAT OF THE SOLDERING IRON.
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4. BEFORE GOING ANY FURTHER YOU HAVE TO ALTER A JUMPER ON THE
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More?
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BOARD SO IT WILL OPERATE WITH THE NEW 256K CHIPS. LOOK IN THE
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APPROXIMATE CENTER OF THE CIRCUT BOARD FOR A SMALL RECTANGLE
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OUTLINED WITH WHITE PAINT. IN THE CENTER OF IT ARE THREE
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SOLDER POINTS.
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EXAMPLE
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_______________
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| O----O O |
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|_______________|
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5. YOU WILL NOTICE THAT THE TWO LEFT HOLES ARE CONNECTED BY A
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JUMPER. THIS SETUP IS SELECTING THE BOARD FOR 64K CHIPS.
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BECAUSE YOU ARE INSTALLING 256K CHIPS YOU HAVE TO JUMP THE
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TWO RIGHT MOST HOLES. CUT THE WIRE LEADING TO THE TWO LEFT
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MOST HOLES AND INSTALL A JUMPER ON THE TWO RIGHT HOLES
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(SOLDER).
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More?
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6.PLUG IN YOUR NEW LARGER (MEMORY) CHIPS INTO THE SOCKETS YOU
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HAVE PREVIOUSLY INSTALLED. THE RECOMMENDED CHIPS ARE:
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256Kx1 DRAMS 150ns
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USE CAUTION WHEN PLUGGING IN YOUR NEW CHIPS SO AS NOT TO BEND
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ANY PINS. I ACCIDENTALLY DID THIS WITH JUST ONE PIN FROM ONE
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CHIP AND THE BOARD FAILED TO FUNCTION. BY RECHECKING MY WORK
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I SAW THAT A LEAD FROM A CHIP BENT UNDERNEATH THE CHIP AND
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FAILED TO GO INTO THE PLUG SOCKET.
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7. NOW GO TO THE ADDRESS SWITCHES TO THE END OF THE CIRCUT
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BOARD. THIS IS THE SMALL BOX WITH FOUR SMALL SWITCHES THAT IS
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VISIBLE TO THE REAR OF THE MODULE. TURN ALL OF THESE SWITCHES
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ON. THIS ALLOW YOUR BOARD TO ANSWER UP AS 512K. REPLACE THE
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CIRCUT BOARD INTO THE MODULE AND PLUG IT IN.
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* Origin: LITTLE BLUE Grand Rapids, Mi. (616) 243-2645 (120/28)
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Read Command [53] 1 - 60, * : ~~ ~~~
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