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Type: Posts; User: Dwight Elvey

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  1. There are a lot of instructions that will work as...

    There are a lot of instructions that will work as good as a NOP. It just needs to be a single machine cycle operation. Most all of the register to register ALU operations are single cycle. That fact...
  2. Power rail always have capacitors on them. These...

    Power rail always have capacitors on them. These can be shorted. Since you have a voltmeter, I'm sure it can read ohms. With the power turned off, measure the resistance from the output of the...
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    Notice the words, "I've been doing that for...

    Notice the words, "I've been doing that for years". Most likely over and over and over.
    I wish there was something one could use on the silver coated mica used in the miniature IF filters. The...
  4. Of course, smaller. I suspect they are out there...

    Of course, smaller. I suspect they are out there someplace. I know some PCs used a similar connector for external drives but I don't know it is was smaller or larger spacing.
    Dwight
  5. I forget what the connectors are called but this...

    I forget what the connectors are called but this looks to be the same style as we often call a centronics printer connector. look through a digikey calalog and you should find something similar....
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    Years ago, I did some experiments. While at...

    Years ago, I did some experiments. While at Intel, I was often reseating things. In some cases, we found that things like using an orange eraser would actually cause later corrosion. It was from the...
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    Which side the cap goes on is usually not...

    Which side the cap goes on is usually not important. There is a slight difference in the low pass as the wipper of the pot is moved from one end to the other, if the capacitor is on the output side...
  8. I gave it a little more thought, read a few...

    I gave it a little more thought, read a few comments and all seem to be assuming it was an integer number issue. It could have just as likely been a floating point number. Floating point numbers have...
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    It is clearly not a printer interface. 7485s are...

    It is clearly not a printer interface. 7485s are magnitude comparitors. There are 8 of them and each compares 4 bits. That would be 32 bits. There doesn't look to be enough wires to send 32 bits from...
  10. Both integer and floating point numbers have...

    Both integer and floating point numbers have their limits in such application. A case in point was using a floating point time accumulator. It needed to be fast, something in the us to ms range....
  11. His application expects an octal stream, not...

    His application expects an octal stream, not binary or S format or Intel Hex.
    One could make a "blue pill" be a translator. It would be trivial code but would require a little circuit to take the...
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    A friend and I were sent to LA for something, I...

    A friend and I were sent to LA for something, I forget what. We stopped at a surplus place. They had about 100 early PETs. I forget which model. They were $30 each. I wasn't interested at the time....
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    He still might add a capacitor. Something like a...

    He still might add a capacitor. Something like a ceramic disk of about 1uF should be fine.
    Dwight
  14. To understand what might be the problem, you have...

    To understand what might be the problem, you have to first understand how the front panel works.
    First, there is likely nothing wrong with the address bus.
    You have something wrong with the examine...
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    I think with the design as shown, A9 and A10...

    I think with the design as shown, A9 and A10 would have allowed interrupts without issues.
    Dwight
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    One wonders why this address range was chosen?...

    One wonders why this address range was chosen? Was there another purpose?
    Dwight
  17. I should also mention that is is not likely the...

    I should also mention that is is not likely the transformer that is the problem. This is because the two higher voltages look good. The transformer is usually wired such that these higher voltages...
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    So it seems that a page 0 access can make about a...

    So it seems that a page 0 access can make about a 2% or better adjustment of the frequency.
    Dwight
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    I wonder how the latch is wired up on the 300....

    I wonder how the latch is wired up on the 300. Will accessing page zero effect it. If not, there are a number of page zero operations that can be used to fine tune, closer than a NOP. The page zero...
  20. Bad diodes will usually show up as 60Hz ripple...

    Bad diodes will usually show up as 60Hz ripple while a bad capacitor will be 120Hz ripple. You need a scope to see this.
    Dwight
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    Even though, I prefer Anchor, the one on 7th...

    Even though, I prefer Anchor, the one on 7th should be visited, as well. It is a large warehouse. You could spend an hour there looking through things. It is on the South-West corner of 7th and Alma....
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    I went to ExcessSolutions and found that they...

    I went to ExcessSolutions and found that they were not interested in selling wire by the foot. I did not try to find and thing like ICs but did walk around. I got the feeling that they were not that...
  23. I assume that meant burst. That would be too slow...

    I assume that meant burst. That would be too slow for distributed that would require 15us between ras refresh pulses for 128 cycle.
    Dwight
  24. It was mentioned that the previous person used a...

    It was mentioned that the previous person used a 8 inch drive. The clock may be at the 8 inch rate, meaning it would be 2X, no matter what the registers were set to in the controller chip. Measure...
  25. Do you know if the DRAM uses distributed or burst...

    Do you know if the DRAM uses distributed or burst refresh. I'd think that with a 8088 one would have enough time between accesses to put distributed refresh.
    Dwight
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