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Tonight (2008-12-30) Josh worked from the backend up a bit, but eventually gave up.  He then moved to the ISA frontside and worked down, which was far more productive.
 
Tonight (2008-12-30) Josh worked from the backend up a bit, but eventually gave up.  He then moved to the ISA frontside and worked down, which was far more productive.
  
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The device appears to sit at ISA IO ports 0x180 through 0x183.  The addresses are decoded by U51 (74688 comparator), which then hits the OE2 on U52-19 (74541 driver iirc).  This is then used to feed U53 and U54 (both 74574 D-flip-flops).  These appear to be there to combat fan-out.  He's not entirely certain where these go, but it seemed like they were going into the RAMs.
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The device appears to sit at ISA IO por<gallery mode="packed-hover">
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File:Ct3-06.jpg|''[[commons:Psetta maxima|Psetta maxima]]'' (Turbot)
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File:044.jpg|''[[commons:Psetta maxima|Psetta maxima]]'' (Turbot)
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File:045.jpg|''[[commons:Psetta maxima|Psetta maxima]]'' (Turbot)
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File:046.jpg|''[[commons:Psetta maxima|Psetta maxima]]'' (Turbot)
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File:047.jpg|''[[commons:Psetta maxima|Psetta maxima]]'' (Turbot)
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File:048.jpg|''[[commons:Psetta maxima|Psetta maxima]]'' (Turbot)
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</gallery>
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ts 0x180 through 0x183.  The addresses are decoded by U51 (74688 comparator), which then hits the OE2 on U52-19 (74541 driver iirc).  This is then used to feed U53 and U54 (both 74574 D-flip-flops).  These appear to be there to combat fan-out.  He's not entirely certain where these go, but it seemed like they were going into the RAMs.
  
 
The low bits of the ISA address selection sit on the rightmost two pins on the top row of the header, SA1 and SA0, in that order (Just hook the connector up and use the multimeter if that's nonsensical).  I haven't traced them through yet; I was in the middle of it when my time ran out.  They look to run over to the empty chip socket on the right side of the board.  Most traces tend to terminate at this chip socket, so most likely we won't be able to use the display logic on the buffer board.
 
The low bits of the ISA address selection sit on the rightmost two pins on the top row of the header, SA1 and SA0, in that order (Just hook the connector up and use the multimeter if that's nonsensical).  I haven't traced them through yet; I was in the middle of it when my time ran out.  They look to run over to the empty chip socket on the right side of the board.  Most traces tend to terminate at this chip socket, so most likely we won't be able to use the display logic on the buffer board.

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