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AOL File Library: 2,801 to 2,900
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aol-file-protocol-4400-2801-to-2900.zip
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TAWUG
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TAWUG Disk No. 22 (SHK)
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TAWUG.22.shk
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MEM.BOARD.PROBS
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.txt
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Wrap
AppleWorks Document
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1986-02-05
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6KB
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82 lines
O=====|====|====|====|====|====|====|====|====|====|====|====|====|====|====|===
Memory Boards and Memory Lapses on my //e
By Bruce R. Mansfield
AIt all started when Jonathan (an overactive five year old guest) (
wanted to play "that flyswatter game".
DBy sheer luck I found the DAUG DOM that contained the program. That G
Ewas when I REALLY decided it was time to catalog not only the club's H
Fdisks, but other all-but-forgotten disks in my collection as well. It H
Fquickly became apparent that a 128K Apple was too small to handle (in ?
memory all at one time) catalog info of the club's 60+ disks.
I was becoming motivated to enter the market for a memory board.
FIn this corner of the world, I found two and a half popular products. I
GTwo of them not only give lots of memory, but also extend the internal G
Elimitations of the AppleWorks program. The third (Apple's own memory H
Fboard) does not (at this time at least) extend the internal limits of B
@AppleWorks. This was important, since I wanted to use the famed I
Gdesktop 3-in-1 program to keep track of my disk collection (if you saw .
my presentation of Quickfile, you know why).
CAt the outset, I wish to thank Fran Wence of Pentagon Enterprises, H
FLisle, Illinois, for his patience in bearing with me as my //e failed D
Bto satisfactorily test memory board after memory board (three new
memory boards, in total).
FWe thought we had an answer for the first one (Checkmate Technology's F
DMULTIRAM board): the company had received a bad batch of chips that @
>caused their board to fail erratically, from time to time. By B
@coincidence, right at this time (Thanksgiving weekend), Applied F
DEngineering made available their latest (RAMWORKS II) memory board, I
Gand so we tried two of those. When they also failed, suspicion fell on H
Fmy //e motherboard (gasp!). These type of products use bank-switching B
@techniques to access the extra memory... BUT the bank switching H
Fcircuits on my motherboard had worked just fine with Apple's extended C
80 column product - flawlessly, over several years of operation.
EConfusion set in as Apple dealer after Apple dealer (4 in total) was D
Bunable to analyze the problem, or take a wild guess as to what he @
>problem might be. The service departments even doubted if the D
Blast-ditch gamble of exchanging the motherboard (@ $180.00) would
solve the problem.
GSupressing growing waves of anxiety, punctuated by occasional pangs of G
Efrustration, I called the Applied Engineering hotline (provided with F
Deach of the Applied Engineering boards). At first, the conversation H
Fwent the same route, but I persisted, focusing our conversation on my
electronics experience.
?After establishing my determination to tackle the problem on a F
Dhardware level, things changed. I asked: "What specific part of the B
@//e motherboard do YOU suspect, given the symptoms that I have I
Gdescribed?" After a short pause, I was given the sage advice to change H
Fout four common, garden-variety chips surrounding the AUX slot. I was H
Ftold that these chips buffer data transmitted through the MMU (Memory H
FManagement Unit - a king-size chip right next to the AUX slot). I was =
given fresh inspiration (not to mention a modicum of hope).
GApparently these 89 cent chips, while failing to meet the needs of the @
>memory boards, were "in-spec" as far as Apple was concerned. G
EAccording to the service departments, if the computer worked ok with H
FApple's extended 80 column card, then it WAS ok . I was told (by each ?
=of the four dealers) that there were no fancy tests for the G
Eparticular circuits under suspicion (or any other circuits, for that
matter).
GObviously, since I'm taking pains to expain all of this, I was able to
solve the problem.
EA $1.50 chip (I paid twice the going rate) set everything right, and G
Eall was forgiven between me and my Apple. Apparently, the chip was a F
Dtad slow for the memory board's liking (even though the extended 80 "
column card didnt seem to mind).
GIf you encounter similiar problems, you might want to have the service G
Edepartment try a similiar experiment (or you can attempt it yourself I
Gif you're careful not to damage the motherboard). Luckily, all four of G
Ethe chips in question were socketed (rather than soldered in place). E
CEven so, I took extreme care to power down first, to discharge ANY D
Bstatic electricity I may have been carrying, and to avoid (at all =
costs) ripping the sockets out of their soldered mountings.
EThe four chips under suspicion cluster around the AUX slot. Three of E
Cthem form a "T" at the rearward end of the AUX slot (that end away G
Efrom the keyboard). These three comprise a 74LS245 flanked by a pair H
Fof 74LS244 chips. The fourth chip (74LS374) lies at the middle of the H
AUX slot, at its right-hand side (this was the culprit in my machine).
FAs a footnote, Applied Engineering identified the 74LS245 chip as the E
Cmost likely offender (curiously enough, this was the same bad chip C
Athat fell into the hands of the hapless manufacturer of my first 4
memory board, MultiRam from Checkmate Technology).
CI never had a lick of trouble since, and the DAUG DOMs are finally
indexed.